; Image Editor
; ------------
; A small multi-window image tool built from the GUI commands and 2D image commands.
;
;   File > Open loads one or more images, each into its own window (or drop image files on a window).
;   Drag on an image to select an area. Drag inside the selection to move it, or drag a grip to resize it.
;   Edit > Copy copies the selection (or the whole image), Edit > Paste puts it into the active image
;   as a floating area you can move and resize. Enter or a click outside applies it; Escape cancels it.
;   Image > Scale resizes the whole image; Image > Crop to Selection crops it.
;   The arrow keys nudge the selection or pasted area by one pixel. The mouse wheel zooms;
;   drag with the right mouse button to scroll a zoomed image.
;   The status bar shows the image size, zoom, cursor position and colour, and the selection or paste
;   rectangle. File > Save writes PNG or BMP.

AppTitle "Image Editor"

Const EVENT_KEY_DOWN=$101
Const EVENT_MOUSE_DOWN=$201
Const EVENT_MOUSE_UP=$202
Const EVENT_MOUSE_MOVE=$203
Const EVENT_MOUSE_WHEEL=$204
Const EVENT_MOUSE_LEAVE=$206
Const EVENT_GADGET_ACTION=$401
Const EVENT_FILE_DROP=$404
Const EVENT_WINDOW_SIZE=$802
Const EVENT_WINDOW_CLOSE=$803
Const EVENT_WINDOW_ACTIVATE=$804
Const EVENT_MENU_ACTION=$1001

Const MENU_OPEN=101
Const MENU_SAVE=102
Const MENU_SAVE_AS=103
Const MENU_CLOSE=104
Const MENU_QUIT=199
Const MENU_UNDO=201
Const MENU_COPY=202
Const MENU_PASTE=203
Const MENU_PASTE_NEW=204
Const MENU_SELECT_ALL=205
Const MENU_DESELECT=206
Const MENU_APPLY_PASTE=207
Const MENU_CANCEL_PASTE=208
Const MENU_PASTE_ORIGINAL_SIZE=209
Const MENU_SCALE=301
Const MENU_CROP=302
Const MENU_ZOOM_IN=401
Const MENU_ZOOM_OUT=402
Const MENU_ACTUAL_SIZE=403
Const MENU_FIT=404
Const MENU_SHORTCUTS=501

Const DRAG_NONE=0
Const DRAG_NEW_SELECTION=1
Const DRAG_SELECTION=2
Const DRAG_PASTE=3
Const DRAG_PAN=4

; Hit-test results: 1-8 are the handles clockwise from the top-left corner, 9 is the inside
Const HIT_INSIDE=9
Const UNDO_LIMIT=20
Const ZOOM_STEPS=17

Type Doc
	Field window,canvas
	Field image,path$,name$,modified,version
	Field zoom#,ox#,oy#
	Field hasSelection,selX,selY,selW,selH
	Field paste,pasteX,pasteY,pasteW,pasteH
	Field view,viewKey$,viewX,viewY
	Field pasteView,pasteViewKey$,pasteViewX,pasteViewY
	Field cursorIn,cursorX,cursorY
	Field note$,dirty
End Type

Type UndoStep
	Field doc.Doc
	Field image
End Type

Global gRunning=True
Global gCurrent.Doc=Null
Global gClipboard=0
Global gUntitled=0
Global gWindowCount=0
Global gLastWheel=0

Global gDragDoc.Doc=Null
Global gDragMode=DRAG_NONE
Global gDragHandle=0
Global gDragStartX#,gDragStartY#
Global gDragX,gDragY,gDragW,gDragH
Global gPanX#,gPanY#

Global gScaleWindow=0
Global gScaleDoc.Doc=Null
Global gScaleWidth,gScaleHeight,gScalePercent,gScaleKeep,gScaleOK,gScaleCancel
Global gScaleLast=0

; Outputs of helper functions that produce more than one value
Global gRenderX,gRenderY
Global gHX,gHY
Global gRX,gRY,gRW,gRH

Dim gZoomStep#(ZOOM_STEPS-1)

Restore ZoomSteps
For i=0 To ZOOM_STEPS-1
	Read gZoomStep(i)
Next

HotKeyEvent 24,2,EVENT_MENU_ACTION,MENU_OPEN          ; Ctrl+O
HotKeyEvent 31,2,EVENT_MENU_ACTION,MENU_SAVE          ; Ctrl+S
HotKeyEvent 31,3,EVENT_MENU_ACTION,MENU_SAVE_AS       ; Ctrl+Shift+S
HotKeyEvent 17,2,EVENT_MENU_ACTION,MENU_CLOSE         ; Ctrl+W
HotKeyEvent 16,2,EVENT_MENU_ACTION,MENU_QUIT          ; Ctrl+Q
HotKeyEvent 44,2,EVENT_MENU_ACTION,MENU_UNDO          ; Ctrl+Z
HotKeyEvent 46,2,EVENT_MENU_ACTION,MENU_COPY          ; Ctrl+C
HotKeyEvent 47,2,EVENT_MENU_ACTION,MENU_PASTE         ; Ctrl+V
HotKeyEvent 47,3,EVENT_MENU_ACTION,MENU_PASTE_NEW     ; Ctrl+Shift+V
HotKeyEvent 30,2,EVENT_MENU_ACTION,MENU_SELECT_ALL    ; Ctrl+A
HotKeyEvent 32,2,EVENT_MENU_ACTION,MENU_DESELECT      ; Ctrl+D
HotKeyEvent 23,3,EVENT_MENU_ACTION,MENU_SCALE         ; Ctrl+Shift+I
HotKeyEvent 46,3,EVENT_MENU_ACTION,MENU_CROP          ; Ctrl+Shift+C
HotKeyEvent 13,2,EVENT_MENU_ACTION,MENU_ZOOM_IN       ; Ctrl+=
HotKeyEvent 12,2,EVENT_MENU_ACTION,MENU_ZOOM_OUT      ; Ctrl+-
HotKeyEvent 11,2,EVENT_MENU_ACTION,MENU_ACTUAL_SIZE   ; Ctrl+0
HotKeyEvent 10,2,EVENT_MENU_ACTION,MENU_FIT           ; Ctrl+9

NewDoc(0,"")
OpenCommandLine

While gRunning
	For d.Doc=Each Doc
		If d\dirty Then DrawDoc d
	Next
	id=WaitEvent()
	While id<>0 And gRunning
		HandleEvent id
		id=PeekEvent()
	Wend
Wend

If gClipboard Then FreeImage gClipboard
End

.ZoomSteps
Data 0.05,0.1,0.125,0.1667,0.25,0.3333,0.5,0.6667,1,1.5,2,3,4,6,8,12,16

;-----------------------------------------------------------------------------
; Events

Function HandleEvent(id)
	src=EventSource()
	If gScaleWindow
		If IsScaleGadget(src)
			HandleScaleEvent id,src
			Return
		EndIf
	EndIf

	d.Doc=DocForGadget(src)
	Select id
	Case EVENT_MENU_ACTION
		RunCommand EventData()
	Case EVENT_WINDOW_CLOSE
		If d<>Null Then CloseDoc d
	Case EVENT_WINDOW_SIZE
		If d<>Null Then d\dirty=True
	Case EVENT_WINDOW_ACTIVATE
		If d<>Null Then gCurrent=d
	Case EVENT_FILE_DROP
		If d<>Null Then OpenPathList EventText(),d
	Case EVENT_MOUSE_DOWN
		If d<>Null
			gCurrent=d
			OnMouseDown d,EventData(),EventX()*Dpi(d),EventY()*Dpi(d)
		EndIf
	Case EVENT_MOUSE_MOVE
		If d<>Null Then OnMouseMove d,EventX()*Dpi(d),EventY()*Dpi(d)
	Case EVENT_MOUSE_UP
		If d<>Null Then OnMouseUp d
	Case EVENT_MOUSE_WHEEL
		If d<>Null Then OnWheel d,EventData()
	Case EVENT_MOUSE_LEAVE
		If d<>Null
			d\cursorIn=False
			UpdateStatus d
		EndIf
	Case EVENT_KEY_DOWN
		If d<>Null Then OnKey d,EventData()
	End Select
End Function

Function RunCommand(command)
	d.Doc=TargetDoc()
	If command=MENU_QUIT
		QuitApp
		Return
	ElseIf command=MENU_SHORTCUTS
		ShowShortcuts
		Return
	EndIf
	If d=Null Then Return
	d\note=""
	Select command
	Case MENU_OPEN : OpenFiles d
	Case MENU_SAVE : SaveDoc d,False
	Case MENU_SAVE_AS : SaveDoc d,True
	Case MENU_CLOSE : CloseDoc d
	Case MENU_UNDO : UndoDoc d
	Case MENU_COPY : CopyArea d
	Case MENU_PASTE : PasteArea d
	Case MENU_PASTE_NEW : PasteAsNewImage
	Case MENU_SELECT_ALL : SelectAll d
	Case MENU_DESELECT : Deselect d
	Case MENU_APPLY_PASTE
		If d\paste Then CommitPaste d
	Case MENU_CANCEL_PASTE
		If d\paste Then CancelPaste d
	Case MENU_PASTE_ORIGINAL_SIZE : PasteOriginalSize d
	Case MENU_SCALE : OpenScaleDialog d
	Case MENU_CROP : CropToSelection d
	Case MENU_ZOOM_IN : ZoomStep d,1,CanvasPixelWidth(d\canvas)/2.0,CanvasPixelHeight(d\canvas)/2.0
	Case MENU_ZOOM_OUT : ZoomStep d,-1,CanvasPixelWidth(d\canvas)/2.0,CanvasPixelHeight(d\canvas)/2.0
	Case MENU_ACTUAL_SIZE : SetZoom d,1,CanvasPixelWidth(d\canvas)/2.0,CanvasPixelHeight(d\canvas)/2.0
	Case MENU_FIT : FitZoom d,True
	End Select
	If DocAlive(d) Then UpdateStatus d
End Function

; The document of the window the user is working in. Menu actions and
; shortcuts carry no source gadget, so they go to the active image window,
; or the last one used while a dialog is in front.
Function TargetDoc.Doc()
	active=ActiveWindow()
	For d.Doc=Each Doc
		If d\window=active Then Return d
	Next
	If gCurrent<>Null Then Return gCurrent
	Return First Doc
End Function

Function DocForGadget.Doc(gadget)
	If gadget=0 Then Return Null
	For d.Doc=Each Doc
		If d\window=gadget Or d\canvas=gadget Then Return d
	Next
	Return Null
End Function

Function DocAlive(target.Doc)
	For d.Doc=Each Doc
		If d=target Then Return True
	Next
	Return False
End Function

;-----------------------------------------------------------------------------
; Windows

Function NewDoc.Doc(image,path$)
	d.Doc=New Doc
	d\image=image
	d\path=path
	d\zoom=1
	If path=""
		gUntitled=gUntitled+1
		d\name="Untitled "+gUntitled
	Else
		d\name=FileName(path)
	EndIf

	width=640
	height=440
	If image
		width=IClamp(ImageWidth(image)+16,420,1100)
		height=IClamp(ImageHeight(image)+16,280,760)
	EndIf
	x=60+(gWindowCount Mod 8)*32
	y=50+(gWindowCount Mod 8)*32
	gWindowCount=gWindowCount+1

	d\window=CreateWindow(d\name,x,y,width,height+60,0,15)
	SetMinWindowSize d\window,320,240
	d\canvas=CreateCanvas(0,0,ClientWidth(d\window),ClientHeight(d\window),d\window)
	SetGadgetLayout d\canvas,1,1,1,1
	EnableGadgetFileDrop d\canvas
	BuildMenus d\window

	If image Then FitZoom d,False
	UpdateTitle d
	UpdateStatus d
	d\dirty=True
	gCurrent=d
	Return d
End Function

Function BuildMenus(window)
	root=WindowMenu(window)
	m=CreateMenu("&File",0,root)
	CreateMenu "&Open...",MENU_OPEN,m
	CreateMenu "&Save",MENU_SAVE,m
	CreateMenu "Save &As...",MENU_SAVE_AS,m
	CreateMenu "",0,m
	CreateMenu "&Close Window",MENU_CLOSE,m
	CreateMenu "E&xit",MENU_QUIT,m

	m=CreateMenu("&Edit",0,root)
	CreateMenu "&Undo",MENU_UNDO,m
	CreateMenu "",0,m
	CreateMenu "&Copy",MENU_COPY,m
	CreateMenu "&Paste",MENU_PASTE,m
	CreateMenu "Paste as &New Image",MENU_PASTE_NEW,m
	CreateMenu "",0,m
	CreateMenu "Apply Paste",MENU_APPLY_PASTE,m
	CreateMenu "Cancel Paste",MENU_CANCEL_PASTE,m
	CreateMenu "Paste at Original Size",MENU_PASTE_ORIGINAL_SIZE,m
	CreateMenu "",0,m
	CreateMenu "Select &All",MENU_SELECT_ALL,m
	CreateMenu "&Deselect",MENU_DESELECT,m

	m=CreateMenu("&Image",0,root)
	CreateMenu "&Scale...",MENU_SCALE,m
	CreateMenu "&Crop to Selection",MENU_CROP,m

	m=CreateMenu("&View",0,root)
	CreateMenu "Zoom &In",MENU_ZOOM_IN,m
	CreateMenu "Zoom &Out",MENU_ZOOM_OUT,m
	CreateMenu "&Actual Size",MENU_ACTUAL_SIZE,m
	CreateMenu "&Fit to Window",MENU_FIT,m

	m=CreateMenu("&Help",0,root)
	CreateMenu "&Keyboard Shortcuts",MENU_SHORTCUTS,m
	UpdateWindowMenu window
End Function

Function UpdateTitle(d.Doc)
	t$=d\name
	If d\image Then t=t+" - "+ImageWidth(d\image)+" x "+ImageHeight(d\image)
	If d\modified Then t=t+" *"
	SetGadgetText d\window,t
End Function

Function CloseDoc(d.Doc)
	If d\modified And d\image<>0
		ActivateWindow d\window
		answer=Proceed("Save changes to "+d\name+" before closing?")
		If answer=-1 Then Return False
		If answer=1
			If Not SaveDoc(d,False) Then Return False
		EndIf
	EndIf
	If gScaleDoc=d Then CloseScaleDialog
	If gDragDoc=d
		gDragDoc=Null
		gDragMode=DRAG_NONE
	EndIf
	For u.UndoStep=Each UndoStep
		If u\doc=d
			FreeImage u\image
			Delete u
		EndIf
	Next
	If d\image Then FreeImage d\image
	If d\paste Then FreeImage d\paste
	If d\view Then FreeImage d\view
	If d\pasteView Then FreeImage d\pasteView
	FreeGadget d\window
	Delete d
	gCurrent=First Doc
	If gCurrent=Null Then gRunning=False
	Return True
End Function

Function QuitApp()
	Repeat
		d.Doc=First Doc
		If d=Null Then Exit
		If Not CloseDoc(d) Then Return
	Forever
	gRunning=False
End Function

Function ShowShortcuts()
	t$="Ctrl (Cmd on a Mac) shortcuts:"+Chr(10)+Chr(10)
	t=t+"O  Open      S  Save      Shift+S  Save As      W  Close"+Chr(10)
	t=t+"Z  Undo      C  Copy      V  Paste      Shift+V  Paste as new image"+Chr(10)
	t=t+"A  Select all      D  Deselect"+Chr(10)
	t=t+"Shift+I  Scale      Shift+C  Crop to selection"+Chr(10)
	t=t+"=  Zoom in      -  Zoom out      0  Actual size      9  Fit"+Chr(10)+Chr(10)
	t=t+"On the image: Enter applies a paste, Escape cancels it or clears the selection,"+Chr(10)
	t=t+"arrow keys nudge by one pixel, the wheel zooms, right-drag scrolls."
	Notify t
End Function

;-----------------------------------------------------------------------------
; Opening and saving

Function OpenFiles(d.Doc)
	files$=RequestFiles("Open images","png;jpg;jpeg;bmp;gif;tga;tif;tiff,*")
	OpenPathList files,d
End Function

Function OpenPathList(items$,target.Doc)
	start=1
	While start<=Len(items)
		separator=Instr(items,Chr(10),start)
		If separator=0 Then separator=Len(items)+1
		path$=Trim(Mid(items,start,separator-start))
		If path<>"" Then OpenPath path,target
		start=separator+1
	Wend
End Function

Function OpenPath(path$,target.Doc)
	image=LoadImage(path)
	If image=0
		Notify "Could not open "+path+Chr(10)+"It may not be an image in a supported format.",True
		Return
	EndIf
	If target<>Null
		If target\image=0
			target\image=image
			target\path=path
			target\name=FileName(path)
			target\modified=False
			target\version=target\version+1
			FitZoom target,False
			UpdateTitle target
			UpdateStatus target
			Return
		EndIf
	EndIf
	NewDoc image,path
End Function

; Files named on the command line open at start-up; quote paths with spaces.
Function OpenCommandLine()
	c$=Trim(CommandLine())
	While c<>""
		If Left(c,1)=Chr(34)
			e=Instr(c,Chr(34),2)
			If e=0 Then e=Len(c)+1
			path$=Mid(c,2,e-2)
			c=Trim(Mid(c,e+1))
		Else
			e=Instr(c," ")
			If e=0 Then e=Len(c)+1
			path$=Mid(c,1,e-1)
			c=Trim(Mid(c,e+1))
		EndIf
		If path<>"" Then OpenPath path,First Doc
	Wend
End Function

Function SaveDoc(d.Doc,saveAs)
	If d\image=0 Then Return False
	If d\paste Then CommitPaste d
	path$=d\path
	ext$=Lower(FileExt(path))
	If saveAs Or path="" Or (ext<>"png" And ext<>"bmp")
		suggested$=d\name
		If FileExt(suggested)<>"" Then suggested=Left(suggested,Len(suggested)-Len(FileExt(suggested))-1)
		path=RequestFile("Save image","png,bmp",True,suggested+".png")
		If path="" Then Return False
		ext=Lower(FileExt(path))
		If ext<>"png" And ext<>"bmp"
			path=path+".png"
			ext="png"
		EndIf
	EndIf
	; SaveImage writes a PNG for a .png name and a BMP for a .bmp name.
	If Not SaveImage(d\image,path)
		Notify "Could not save "+path,True
		Return False
	EndIf
	d\path=path
	d\name=FileName(path)
	d\modified=False
	d\note="Saved "+d\name
	UpdateTitle d
	UpdateStatus d
	Return True
End Function

Function FileName$(path$)
	For i=Len(path) To 1 Step -1
		c$=Mid(path,i,1)
		If c="/" Or c="\" Then Return Mid(path,i+1)
	Next
	Return path
End Function

Function FileExt$(path$)
	name$=FileName(path)
	For i=Len(name) To 1 Step -1
		If Mid(name,i,1)="." Then Return Mid(name,i+1)
	Next
	Return ""
End Function

;-----------------------------------------------------------------------------
; Drawing

Function Dpi#(d.Doc)
	w=GadgetWidth(d\canvas)
	If w<=0 Then Return 1
	r#=Float(CanvasPixelWidth(d\canvas))/w
	If r<=0 Then Return 1
	Return r
End Function

; Canvas pixels per image pixel. 100% zoom shows one image pixel per logical
; screen pixel, so images keep their size on high-DPI displays.
Function ViewScale#(d.Doc)
	Return d\zoom*Dpi(d)
End Function

Function DrawDoc(d.Doc)
	d\dirty=False
	SetBuffer CanvasBuffer(d\canvas)
	cw=CanvasPixelWidth(d\canvas)
	ch=CanvasPixelHeight(d\canvas)
	ClsColor 46,46,52
	Cls
	If d\image=0
		Color 190,190,200
		Text cw/2,ch/2-FontHeight(),"No image open",True,True
		Text cw/2,ch/2+FontHeight(),"Choose File > Open, or drop image files here",True,True
		FlipCanvas d\canvas
		Return
	EndIf

	ClampView d
	s#=ViewScale(d)
	iw#=ImageWidth(d\image)*s
	ih#=ImageHeight(d\image)*s

	viewKey$=d\version+":"+s+":"+d\ox+":"+d\oy+":"+cw+":"+ch
	If viewKey<>d\viewKey
		If d\view Then FreeImage d\view
		d\view=RenderClipped(d\image,d\ox,d\oy,iw,ih,cw,ch,s<1)
		d\viewX=gRenderX
		d\viewY=gRenderY
		d\viewKey=viewKey
	EndIf
	Color 18,18,20
	Rect Floor(d\ox)-1,Floor(d\oy)-1,Floor(d\ox+iw)-Floor(d\ox)+2,Floor(d\oy+ih)-Floor(d\oy)+2,False
	If d\view Then DrawBlock d\view,d\viewX,d\viewY

	If d\paste
		px#=d\ox+d\pasteX*s
		py#=d\oy+d\pasteY*s
		pw#=d\pasteW*s
		ph#=d\pasteH*s
		viewKey=d\paste+":"+px+":"+py+":"+pw+":"+ph+":"+cw+":"+ch
		If viewKey<>d\pasteViewKey
			If d\pasteView Then FreeImage d\pasteView
			d\pasteView=RenderClipped(d\paste,px,py,pw,ph,cw,ch,s*d\pasteW/ImageWidth(d\paste)<1)
			d\pasteViewX=gRenderX
			d\pasteViewY=gRenderY
			d\pasteViewKey=viewKey
		EndIf
		If d\pasteView Then DrawBlock d\pasteView,d\pasteViewX,d\pasteViewY
		DrawFrame d,d\pasteX,d\pasteY,d\pasteW,d\pasteH,False
	ElseIf d\hasSelection
		DrawFrame d,d\selX,d\selY,d\selW,d\selH,True
	EndIf
	FlipCanvas d\canvas
End Function

; Renders the part of an image that falls inside the canvas, scaled to the
; rectangle x,y,w,h in canvas pixels. Only the visible part is resized, so
; deep zooms stay cheap. Returns 0 when nothing is visible.
Function RenderClipped(source,x#,y#,w#,h#,cw,ch,smooth)
	sw=ImageWidth(source)
	sh=ImageHeight(source)
	kx#=w/sw
	ky#=h/sh
	x0=IMax(0,Floor(-x/kx))
	y0=IMax(0,Floor(-y/ky))
	x1=IMin(sw,Ceil((cw-x)/kx))
	y1=IMin(sh,Ceil((ch-y)/ky))
	If x1<=x0 Or y1<=y0 Then Return 0
	rw=x1-x0
	rh=y1-y0
	gRenderX=Floor(x+x0*kx)
	gRenderY=Floor(y+y0*ky)
	dw=IMax(1,Floor(x+x1*kx)-gRenderX)
	dh=IMax(1,Floor(y+y1*ky)-gRenderY)
	region=CreateImage(rw,rh)
	CopyRect x0,y0,rw,rh,0,0,ImageBuffer(source),ImageBuffer(region)
	If dw<>rw Or dh<>rh
		TFormFilter smooth
		ResizeImage region,dw,dh
	EndIf
	Return region
End Function

; Draws a selection (dashed) or pasted area (solid) with its resize handles
; and a size label.
Function DrawFrame(d.Doc,x,y,w,h,dashed)
	s#=ViewScale(d)
	x0=Floor(d\ox+x*s)
	y0=Floor(d\oy+y*s)
	x1=Floor(d\ox+(x+w)*s)
	y1=Floor(d\oy+(y+h)*s)
	fw=IMax(1,x1-x0)
	fh=IMax(1,y1-y0)
	If dashed
		Color 0,0,0
		Rect x0,y0,fw,fh,False
		Color 255,255,255
		For i=0 To fw-1 Step 8
			Line x0+i,y0,x0+IMin(i+3,fw-1),y0
			Line x0+i,y0+fh-1,x0+IMin(i+3,fw-1),y0+fh-1
		Next
		For i=0 To fh-1 Step 8
			Line x0,y0+i,x0,y0+IMin(i+3,fh-1)
			Line x0+fw-1,y0+i,x0+fw-1,y0+IMin(i+3,fh-1)
		Next
	Else
		Color 0,0,0
		Rect x0-1,y0-1,fw+2,fh+2,False
		Color 70,160,255
		Rect x0,y0,fw,fh,False
	EndIf

	hs=IMax(3,Floor(3.5*Dpi(d)))
	For i=1 To 8
		HandlePosition i,x0,y0,x0+fw,y0+fh
		Color 0,0,0
		Rect gHX-hs-1,gHY-hs-1,hs*2+3,hs*2+3,True
		Color 255,255,255
		Rect gHX-hs,gHY-hs,hs*2+1,hs*2+1,True
	Next

	label$=w+" x "+h+"  at "+x+", "+y
	lw=StringWidth(label)+8
	lh=FontHeight()+4
	ly=y0+fh+hs+4
	If ly+lh>CanvasPixelHeight(d\canvas) Then ly=y0-lh-hs-4
	lx=IClamp(x0,0,IMax(0,CanvasPixelWidth(d\canvas)-lw))
	Color 0,0,0
	Rect lx,ly,lw,lh,True
	Color 255,255,255
	Text lx+4,ly+2,label
End Function

Function HandlePosition(i,x0,y0,x1,y1)
	mx=(x0+x1)/2
	my=(y0+y1)/2
	Select i
	Case 1 : gHX=x0 : gHY=y0
	Case 2 : gHX=mx : gHY=y0
	Case 3 : gHX=x1 : gHY=y0
	Case 4 : gHX=x1 : gHY=my
	Case 5 : gHX=x1 : gHY=y1
	Case 6 : gHX=mx : gHY=y1
	Case 7 : gHX=x0 : gHY=y1
	Case 8 : gHX=x0 : gHY=my
	End Select
End Function

; Which grip (1-8) or the inside (HIT_INSIDE) of an image rectangle is under
; canvas pixel px,py; 0 for none.
Function HitTest(d.Doc,x,y,w,h,px#,py#)
	s#=ViewScale(d)
	x0=Floor(d\ox+x*s)
	y0=Floor(d\oy+y*s)
	x1=x0+IMax(1,Floor(d\ox+(x+w)*s)-x0)
	y1=y0+IMax(1,Floor(d\oy+(y+h)*s)-y0)
	reach#=6*Dpi(d)
	For i=1 To 8
		HandlePosition i,x0,y0,x1,y1
		If Abs(px-gHX)<=reach And Abs(py-gHY)<=reach Then Return i
	Next
	If px>=x0 And px<x1 And py>=y0 And py<y1 Then Return HIT_INSIDE
	Return 0
End Function

;-----------------------------------------------------------------------------
; View

; Centres an image smaller than the canvas and keeps a larger one covering it.
Function ClampView(d.Doc)
	If d\image=0 Then Return
	s#=ViewScale(d)
	iw#=ImageWidth(d\image)*s
	ih#=ImageHeight(d\image)*s
	cw=CanvasPixelWidth(d\canvas)
	ch=CanvasPixelHeight(d\canvas)
	If iw<=cw
		d\ox=Floor((cw-iw)/2)
	Else
		d\ox=FClamp(d\ox,cw-iw,0)
	EndIf
	If ih<=ch
		d\oy=Floor((ch-ih)/2)
	Else
		d\oy=FClamp(d\oy,ch-ih,0)
	EndIf
End Function

; Zooms so that canvas pixel px,py stays over the same image pixel.
Function SetZoom(d.Doc,zoom#,px#,py#)
	If d\image=0 Then Return
	s#=ViewScale(d)
	ix#=(px-d\ox)/s
	iy#=(py-d\oy)/s
	d\zoom=FClamp(zoom,gZoomStep(0),gZoomStep(ZOOM_STEPS-1))
	s=ViewScale(d)
	d\ox=px-ix*s
	d\oy=py-iy*s
	ClampView d
	d\dirty=True
End Function

Function ZoomStep(d.Doc,direction,px#,py#)
	If direction>0
		For i=0 To ZOOM_STEPS-1
			If gZoomStep(i)>d\zoom*1.01
				SetZoom d,gZoomStep(i),px,py
				Return
			EndIf
		Next
	Else
		For i=ZOOM_STEPS-1 To 0 Step -1
			If gZoomStep(i)<d\zoom*0.99
				SetZoom d,gZoomStep(i),px,py
				Return
			EndIf
		Next
	EndIf
End Function

Function FitZoom(d.Doc,allowEnlarge)
	If d\image=0 Then Return
	cw#=GadgetWidth(d\canvas)-16
	ch#=GadgetHeight(d\canvas)-16
	zoom#=FMin(cw/ImageWidth(d\image),ch/ImageHeight(d\image))
	If zoom>1 And (Not allowEnlarge) Then zoom=1
	d\zoom=FClamp(zoom,gZoomStep(0),gZoomStep(ZOOM_STEPS-1))
	d\ox=0
	d\oy=0
	ClampView d
	d\dirty=True
End Function

;-----------------------------------------------------------------------------
; Mouse and keyboard

Function OnMouseDown(d.Doc,button,px#,py#)
	ActivateGadget d\canvas
	d\note=""
	If d\image=0 Then Return
	s#=ViewScale(d)
	ix#=(px-d\ox)/s
	iy#=(py-d\oy)/s

	If button<>1
		BeginDrag d,DRAG_PAN,0,px,py,0,0,0,0
		gPanX=d\ox
		gPanY=d\oy
		Return
	EndIf

	If d\paste
		hit=HitTest(d,d\pasteX,d\pasteY,d\pasteW,d\pasteH,px,py)
		If hit
			BeginDrag d,DRAG_PASTE,hit,ix,iy,d\pasteX,d\pasteY,d\pasteW,d\pasteH
			Return
		EndIf
		; A click outside the pasted area applies it.
		CommitPaste d
		d\hasSelection=False
		UpdateStatus d
		Return
	EndIf

	If d\hasSelection
		hit=HitTest(d,d\selX,d\selY,d\selW,d\selH,px,py)
		If hit
			BeginDrag d,DRAG_SELECTION,hit,ix,iy,d\selX,d\selY,d\selW,d\selH
			Return
		EndIf
	EndIf

	ax=IClamp(Floor(ix+0.5),0,ImageWidth(d\image))
	ay=IClamp(Floor(iy+0.5),0,ImageHeight(d\image))
	BeginDrag d,DRAG_NEW_SELECTION,0,ix,iy,ax,ay,0,0
	d\hasSelection=False
	d\dirty=True
	UpdateStatus d
End Function

Function BeginDrag(d.Doc,mode,grip,startX#,startY#,x,y,w,h)
	gDragDoc=d
	gDragMode=mode
	gDragHandle=grip
	gDragStartX=startX
	gDragStartY=startY
	gDragX=x
	gDragY=y
	gDragW=w
	gDragH=h
End Function

Function OnMouseMove(d.Doc,px#,py#)
	If d\image=0 Then Return
	s#=ViewScale(d)
	ix#=(px-d\ox)/s
	iy#=(py-d\oy)/s
	d\cursorIn=True
	d\cursorX=Floor(ix)
	d\cursorY=Floor(iy)

	If gDragDoc=d
		iw=ImageWidth(d\image)
		ih=ImageHeight(d\image)
		dx=Floor(ix-gDragStartX+0.5)
		dy=Floor(iy-gDragStartY+0.5)
		Select gDragMode
		Case DRAG_PAN
			d\ox=gPanX+px-gDragStartX
			d\oy=gPanY+py-gDragStartY
			ClampView d
		Case DRAG_NEW_SELECTION
			cx=IClamp(Floor(ix+0.5),0,iw)
			cy=IClamp(Floor(iy+0.5),0,ih)
			d\selX=IMin(gDragX,cx)
			d\selY=IMin(gDragY,cy)
			d\selW=Abs(cx-gDragX)
			d\selH=Abs(cy-gDragY)
			d\hasSelection=(d\selW>0 And d\selH>0)
		Case DRAG_SELECTION
			If gDragHandle=HIT_INSIDE
				d\selX=IClamp(gDragX+dx,0,iw-gDragW)
				d\selY=IClamp(gDragY+dy,0,ih-gDragH)
			Else
				ResizeRect gDragHandle,gDragX,gDragY,gDragW,gDragH,dx,dy
				ClampRectToImage d
				d\selX=gRX
				d\selY=gRY
				d\selW=gRW
				d\selH=gRH
			EndIf
		Case DRAG_PASTE
			If gDragHandle=HIT_INSIDE
				d\pasteX=gDragX+dx
				d\pasteY=gDragY+dy
			Else
				ResizeRect gDragHandle,gDragX,gDragY,gDragW,gDragH,dx,dy
				d\pasteX=gRX
				d\pasteY=gRY
				d\pasteW=gRW
				d\pasteH=gRH
			EndIf
		End Select
		d\dirty=True
	EndIf
	UpdateStatus d
End Function

Function OnMouseUp(d.Doc)
	If gDragDoc=d
		gDragDoc=Null
		gDragMode=DRAG_NONE
		UpdateStatus d
	EndIf
End Function

Function OnWheel(d.Doc,detents)
	If d\image=0 Or detents=0 Then Return
	; Trackpads send a burst of wheel events; take one zoom step per burst.
	If MilliSecs()-gLastWheel<60 Then Return
	gLastWheel=MilliSecs()
	ZoomStep d,Sgn(detents),CanvasMouseX(d\canvas),CanvasMouseY(d\canvas)
	UpdateStatus d
End Function

Function OnKey(d.Doc,key)
	If d\image=0 Then Return
	dx=0
	dy=0
	Select key
	Case 1
		If d\paste
			CancelPaste d
		Else
			d\hasSelection=False
		EndIf
	Case 28,156
		If d\paste Then CommitPaste d
	Case 203 : dx=-1
	Case 205 : dx=1
	Case 200 : dy=-1
	Case 208 : dy=1
	End Select
	If dx<>0 Or dy<>0
		If d\paste
			d\pasteX=d\pasteX+dx
			d\pasteY=d\pasteY+dy
		ElseIf d\hasSelection
			d\selX=IClamp(d\selX+dx,0,ImageWidth(d\image)-d\selW)
			d\selY=IClamp(d\selY+dy,0,ImageHeight(d\image)-d\selH)
		EndIf
	EndIf
	d\dirty=True
	UpdateStatus d
End Function

; Moves the edges of a rectangle named by a grip; the result is in gRX..gRH.
Function ResizeRect(grip,x,y,w,h,dx,dy)
	x0=x
	y0=y
	x1=x+w
	y1=y+h
	If grip=1 Or grip=7 Or grip=8 Then x0=x0+dx
	If grip=3 Or grip=4 Or grip=5 Then x1=x1+dx
	If grip=1 Or grip=2 Or grip=3 Then y0=y0+dy
	If grip=5 Or grip=6 Or grip=7 Then y1=y1+dy
	gRX=IMin(x0,x1)
	gRY=IMin(y0,y1)
	gRW=IMax(1,Abs(x1-x0))
	gRH=IMax(1,Abs(y1-y0))
End Function

Function ClampRectToImage(d.Doc)
	iw=ImageWidth(d\image)
	ih=ImageHeight(d\image)
	x0=IClamp(gRX,0,iw-1)
	y0=IClamp(gRY,0,ih-1)
	gRW=IMax(1,IMin(gRX+gRW,iw)-x0)
	gRH=IMax(1,IMin(gRY+gRH,ih)-y0)
	gRX=x0
	gRY=y0
End Function

Function UpdateStatus(d.Doc)
	If d\image=0
		SetStatusText d\window,"No image - File > Open, or drop image files on the window"
		Return
	EndIf
	iw=ImageWidth(d\image)
	ih=ImageHeight(d\image)
	t$=iw+" x "+ih+" px    Zoom "+Int(d\zoom*100)+"%"
	If d\cursorIn And d\cursorX>=0 And d\cursorY>=0 And d\cursorX<iw And d\cursorY<ih
		rgb=ReadPixel(d\cursorX,d\cursorY,ImageBuffer(d\image))
		t=t+"    Cursor "+d\cursorX+", "+d\cursorY
		t=t+"    RGB "+((rgb Shr 16) And 255)+", "+((rgb Shr 8) And 255)+", "+(rgb And 255)
	EndIf
	If d\paste
		t=t+"    Paste "+d\pasteW+" x "+d\pasteH+" at "+d\pasteX+", "+d\pasteY
		sx=Int(100.0*d\pasteW/ImageWidth(d\paste))
		sy=Int(100.0*d\pasteH/ImageHeight(d\paste))
		If sx=sy
			t=t+" ("+sx+"%)"
		Else
			t=t+" ("+sx+"% x "+sy+"%)"
		EndIf
	ElseIf d\hasSelection
		t=t+"    Selection "+d\selW+" x "+d\selH+" at "+d\selX+", "+d\selY
		t=t+" to "+(d\selX+d\selW)+", "+(d\selY+d\selH)
	EndIf
	If d\note<>"" Then t=t+"    "+d\note
	SetStatusText d\window,t
End Function

;-----------------------------------------------------------------------------
; Editing

Function MarkChanged(d.Doc)
	d\modified=True
	d\version=d\version+1
	d\dirty=True
	UpdateTitle d
End Function

Function PushUndo(d.Doc)
	u.UndoStep=New UndoStep
	u\doc=d
	u\image=CopyImage(d\image)
	count=0
	For u=Each UndoStep
		If u\doc=d Then count=count+1
	Next
	If count>UNDO_LIMIT
		For u=Each UndoStep
			If u\doc=d
				FreeImage u\image
				Delete u
				Exit
			EndIf
		Next
	EndIf
End Function

Function UndoDoc(d.Doc)
	If d\paste
		CancelPaste d
		Return
	EndIf
	newest.UndoStep=Null
	For u.UndoStep=Each UndoStep
		If u\doc=d Then newest=u
	Next
	If newest=Null
		d\note="Nothing to undo"
		Return
	EndIf
	If d\image Then FreeImage d\image
	d\image=newest\image
	Delete newest
	d\hasSelection=False
	MarkChanged d
	ClampView d
End Function

Function SelectAll(d.Doc)
	If d\image=0 Then Return
	If d\paste Then CommitPaste d
	d\selX=0
	d\selY=0
	d\selW=ImageWidth(d\image)
	d\selH=ImageHeight(d\image)
	d\hasSelection=True
	d\dirty=True
End Function

Function Deselect(d.Doc)
	If d\paste Then CommitPaste d
	d\hasSelection=False
	d\dirty=True
End Function

Function ScaledCopy(source,w,h)
	result=CopyImage(source)
	If ImageWidth(result)<>w Or ImageHeight(result)<>h
		TFormFilter True
		ResizeImage result,w,h
	EndIf
	Return result
End Function

; Copies the pasted area at its current size, else the selection, else the whole image.
Function CopyArea(d.Doc)
	If d\image=0 Then Return
	If gClipboard Then FreeImage gClipboard
	If d\paste
		gClipboard=ScaledCopy(d\paste,d\pasteW,d\pasteH)
	ElseIf d\hasSelection
		gClipboard=CreateImage(d\selW,d\selH)
		CopyRect d\selX,d\selY,d\selW,d\selH,0,0,ImageBuffer(d\image),ImageBuffer(gClipboard)
	Else
		gClipboard=CopyImage(d\image)
	EndIf
	d\note="Copied "+ImageWidth(gClipboard)+" x "+ImageHeight(gClipboard)
End Function

; Pastes as a floating area over the selection, or in the middle of the view.
Function PasteArea(d.Doc)
	If gClipboard=0
		d\note="Nothing to paste - copy an area first"
		Return
	EndIf
	If d\image=0
		d\image=CopyImage(gClipboard)
		MarkChanged d
		FitZoom d,False
		Return
	EndIf
	If d\paste Then CommitPaste d
	d\paste=CopyImage(gClipboard)
	d\pasteW=ImageWidth(d\paste)
	d\pasteH=ImageHeight(d\paste)
	If d\hasSelection
		d\pasteX=d\selX
		d\pasteY=d\selY
	Else
		s#=ViewScale(d)
		cx=IClamp(Floor((CanvasPixelWidth(d\canvas)/2-d\ox)/s),0,ImageWidth(d\image))
		cy=IClamp(Floor((CanvasPixelHeight(d\canvas)/2-d\oy)/s),0,ImageHeight(d\image))
		d\pasteX=cx-d\pasteW/2
		d\pasteY=cy-d\pasteH/2
	EndIf
	d\hasSelection=False
	d\note="Drag to move, drag the handles to resize, Enter to apply"
	d\dirty=True
End Function

Function PasteAsNewImage()
	If gClipboard=0
		Notify "Nothing to paste - copy an area first."
		Return
	EndIf
	d.Doc=NewDoc(CopyImage(gClipboard),"")
	d\modified=True
	UpdateTitle d
End Function

Function PasteOriginalSize(d.Doc)
	If d\paste=0 Then Return
	d\pasteW=ImageWidth(d\paste)
	d\pasteH=ImageHeight(d\paste)
	d\dirty=True
End Function

; Stamps the floating pasted area into the image; it stays selected.
Function CommitPaste(d.Doc)
	If d\paste=0 Then Return
	PushUndo d
	stamp=ScaledCopy(d\paste,d\pasteW,d\pasteH)
	iw=ImageWidth(d\image)
	ih=ImageHeight(d\image)
	sx=0
	sy=0
	dx=d\pasteX
	dy=d\pasteY
	w=ImageWidth(stamp)
	h=ImageHeight(stamp)
	If dx<0
		sx=-dx
		w=w+dx
		dx=0
	EndIf
	If dy<0
		sy=-dy
		h=h+dy
		dy=0
	EndIf
	w=IMin(w,iw-dx)
	h=IMin(h,ih-dy)
	d\hasSelection=False
	If w>0 And h>0
		CopyRect sx,sy,w,h,dx,dy,ImageBuffer(stamp),ImageBuffer(d\image)
		d\selX=dx
		d\selY=dy
		d\selW=w
		d\selH=h
		d\hasSelection=True
	EndIf
	FreeImage stamp
	FreeImage d\paste
	d\paste=0
	MarkChanged d
End Function

Function CancelPaste(d.Doc)
	If d\paste=0 Then Return
	FreeImage d\paste
	d\paste=0
	d\dirty=True
End Function

Function CropToSelection(d.Doc)
	If d\image=0 Then Return
	If d\paste Then CommitPaste d
	If Not d\hasSelection
		Notify "Select an area to crop to first: drag on the image."
		Return
	EndIf
	PushUndo d
	cropped=CreateImage(d\selW,d\selH)
	CopyRect d\selX,d\selY,d\selW,d\selH,0,0,ImageBuffer(d\image),ImageBuffer(cropped)
	FreeImage d\image
	d\image=cropped
	d\hasSelection=False
	MarkChanged d
	ClampView d
End Function

;-----------------------------------------------------------------------------
; Scale dialog

Function OpenScaleDialog(d.Doc)
	If d\image=0 Then Return
	If d\paste Then CommitPaste d
	If gScaleWindow Then CloseScaleDialog
	gScaleDoc=d
	iw=ImageWidth(d\image)
	ih=ImageHeight(d\image)
	gScaleWindow=CreateWindow("Scale Image",GadgetX(d\window)+60,GadgetY(d\window)+60,300,250,d\window,1)
	CreateLabel "Current size: "+iw+" x "+ih+" pixels",16,14,268,20,gScaleWindow
	CreateLabel "Width",16,48,70,20,gScaleWindow
	gScaleWidth=CreateSpinBox(90,44,110,24,gScaleWindow)
	CreateLabel "pixels",208,48,70,20,gScaleWindow
	CreateLabel "Height",16,80,70,20,gScaleWindow
	gScaleHeight=CreateSpinBox(90,76,110,24,gScaleWindow)
	CreateLabel "pixels",208,80,70,20,gScaleWindow
	CreateLabel "Percent",16,112,70,20,gScaleWindow
	gScalePercent=CreateSpinBox(90,108,110,24,gScaleWindow)
	CreateLabel "%",208,112,70,20,gScaleWindow
	gScaleKeep=CreateButton("Keep proportions",16,142,260,22,gScaleWindow,2)
	SetButtonState gScaleKeep,True
	gScaleCancel=CreateButton("Cancel",104,178,84,28,gScaleWindow,5)
	gScaleOK=CreateButton("Scale",196,178,84,28,gScaleWindow,4)
	SetSpinBoxRange gScaleWidth,1,16384
	SetSpinBoxRange gScaleHeight,1,16384
	SetSpinBoxRange gScalePercent,1,1000
	SetSpinBoxValue gScaleWidth,iw
	SetSpinBoxValue gScaleHeight,ih
	SetSpinBoxValue gScalePercent,100
	gScaleLast=0
	ActivateGadget gScaleWidth
End Function

Function IsScaleGadget(gadget)
	If gadget=0 Then Return False
	Select gadget
	Case gScaleWindow,gScaleWidth,gScaleHeight,gScalePercent,gScaleKeep,gScaleOK,gScaleCancel
		Return True
	End Select
	Return False
End Function

Function HandleScaleEvent(id,source)
	If id=EVENT_WINDOW_CLOSE
		CloseScaleDialog
		Return
	EndIf
	If id<>EVENT_GADGET_ACTION Then Return
	Select source
	Case gScaleWidth
		gScaleLast=0
		SyncScaleFields
	Case gScaleHeight
		gScaleLast=1
		SyncScaleFields
	Case gScalePercent
		gScaleLast=2
		SyncScaleFields
	Case gScaleKeep
		SyncScaleFields
	Case gScaleOK
		SyncScaleFields
		ApplyScale gScaleDoc,SpinBoxValue(gScaleWidth),SpinBoxValue(gScaleHeight)
		CloseScaleDialog
	Case gScaleCancel
		CloseScaleDialog
	End Select
End Function

; Fills the other fields from the one edited last.
Function SyncScaleFields()
	iw#=ImageWidth(gScaleDoc\image)
	ih#=ImageHeight(gScaleDoc\image)
	w=SpinBoxValue(gScaleWidth)
	h=SpinBoxValue(gScaleHeight)
	keep=ButtonState(gScaleKeep)
	If gScaleLast=2
		p#=SpinBoxValue(gScalePercent)/100.0
		w=IMax(1,Int(iw*p))
		h=IMax(1,Int(ih*p))
	ElseIf keep And gScaleLast=1
		w=IMax(1,Int(h*iw/ih))
	ElseIf keep
		h=IMax(1,Int(w*ih/iw))
	EndIf
	SetSpinBoxValue gScaleWidth,w
	SetSpinBoxValue gScaleHeight,h
	If gScaleLast<>2 Then SetSpinBoxValue gScalePercent,Int(100.0*w/iw)
End Function

Function ApplyScale(d.Doc,w,h)
	If w=ImageWidth(d\image) And h=ImageHeight(d\image) Then Return
	PushUndo d
	TFormFilter True
	ResizeImage d\image,w,h
	d\hasSelection=False
	d\note="Scaled to "+ImageWidth(d\image)+" x "+ImageHeight(d\image)
	MarkChanged d
	ClampView d
	UpdateStatus d
End Function

Function CloseScaleDialog()
	If gScaleWindow=0 Then Return
	FreeGadget gScaleWindow
	gScaleWindow=0
	If gScaleDoc<>Null Then ActivateWindow gScaleDoc\window
	gScaleDoc=Null
End Function

;-----------------------------------------------------------------------------
; Maths

Function IMin(a,b)
	If a<b Then Return a
	Return b
End Function

Function IMax(a,b)
	If a>b Then Return a
	Return b
End Function

Function IClamp(v,low,high)
	If v<low Then Return low
	If v>high Then Return high
	Return v
End Function

Function FMin#(a#,b#)
	If a<b Then Return a
	Return b
End Function

Function FClamp#(v#,low#,high#)
	If v<low Then Return low
	If v>high Then Return high
	Return v
End Function