FillArea() inside ClipOutput() does not work

[nicoh]

Hello,

I guess there is a bug in FillArea() when the drawing output is clipped.

Code: Select all

EnableExplicit

OpenWindow(0, 0, 0, 400, 400, "FillArea() Bug", #PB_Window_ScreenCentered | #PB_Window_SystemMenu)
CanvasGadget(0, 0, 0, 400, 400)

If StartDrawing(CanvasOutput(0))
  Box(0, 0, 400, 400, #Green)
  ClipOutput(100, 100, 200, 200)  ; Clips the output to a 200x200 square
  FillArea(50, 50, #Blue, #Blue)  ; The 200x200 square should be painted blue (but nothing is painted blue)
  UnclipOutput()
  StopDrawing()
EndIf

Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow

Shouldn't there be an inner square drawn in blue?

If you remove the "ClipOutput()", the whole window is painted blue.
So when clipping the output, there should be an inner square painted blue? Where is it?

In my real program (which is a bit more complex than this sample program) the program even crashes at this point with a "random" memory error or the executable ends unexpectedly. Unfortunately I could not reproduce this crash specifically in a sample program, but I am relatively sure that the crash comes from FillArea(). If I comment out FillArea() in my real program, it no longer crashes.

EDIT: Now I am able to reproduce the crash in a sample program. See posting below.

Maybe someone who has insight into the implementation of FillArea() can check this?

// Moved from "Bugs - Windows" to "Coding Questions" (Kiffi)

[Mijikai]

No Bug!

From the help:

The drawing origin is not modified by a call to this function. To make all drawing relative to the upper left corner of the clipping box, a separate call to SetOrigin() must be made if this is desired

Either use SetOrigin() or Fill(100,100,...

[nicoh]

No Bug!

From the help: [...]

I know the origin (50,50) is outside the clipped area.

when replacing FillArea() with Box(0, 0, 400, 400, #Blue) the inner square is still painted blue, even if the (0,0) point is outside the clipped area.
Same thing when drawing lines, circles etc ... every drawing operation which starts outside the clipped area is still drawn inside the area.

So why doesn't the same thing happens to FillArea() ?
I guess this is a bug or at least inconsistent.

[nicoh]

Hello,

now I am able to reproduce the crash!

Code: Select all

EnableExplicit

OpenWindow(0, 0, 0, 400, 400, "FillArea() Bug", #PB_Window_ScreenCentered | #PB_Window_SystemMenu)
CanvasGadget(0, 0, 0, 400, 400)

If StartDrawing(CanvasOutput(0))
  
  ClipOutput(248,-50,30,54)
  FillArea(277,3,$FF,$FF)
  UnclipOutput()
  
  ClipOutput(248,68,30,54)
  FillArea(277,121,$FF,$FF)
  UnclipOutput()
  
  ClipOutput(248,127,30,54)
  FillArea(277,180,$FF,$FF)
  UnclipOutput()
  
  StopDrawing()
EndIf

Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow

This code crashes with "Invalid memory access".

[Marc56us]

now I am able to reproduce the crash!

Code: Select all

ClipOutput(248,-50,30,54)

Not a bug: beware of typing errors: -50
F1
ClipOutput()
The (x, y) coordinates are always absolute [...]

[nicoh]

Not a bug: beware of typing errors: -50
F1
ClipOutput()
The (x, y) coordinates are always absolute [...]

Okay, that's a calculation error in my program. The value should not be smaller then 0. I agree.
But still ... there should not be a Memory Error since I don't do any memory operations?

[Mijikai]

In order to be fast some drawing functions wont perform boudary checks, so you might end up drawing in arbitrary memory which is bad.

[nicoh]

So, I added boundary checks to my programm but it still crashes with a memory error.

Code: Select all

EnableExplicit

OpenWindow(0, 0, 0, 800, 800, "FillArea() Bug", #PB_Window_ScreenCentered | #PB_Window_SystemMenu)
CanvasGadget(0, 0, 0, 800, 800)

If StartDrawing(CanvasOutput(0))
  
  ClipOutput(248, 0, 30, 46)
  FillArea(277, 9, $FF0000, $FF0000)
  UnclipOutput()
  
  ClipOutput(248, 51, 30, 54)
  FillArea(277, 68, $FF0000, $FF0000)
  UnclipOutput()
  
  StopDrawing()
EndIf

Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow

Any ideas?

[RASHAD]

Hi

Code: Select all

EnableExplicit

OpenWindow(0, 0, 0, 800, 800, "FillArea() Bug", #PB_Window_ScreenCentered | #PB_Window_SystemMenu)
CanvasGadget(0, 0, 0, 800, 800)

If StartDrawing(CanvasOutput(0))
  
  ClipOutput(248, 100, 30, 54)
  FillArea(277, 110, $FF0000, $FF0000)
  UnclipOutput()
  
  ClipOutput(248, 50, 30, 46)
  FillArea(277, 55, $0000FF, $0000FF)
  UnclipOutput()
  
  ClipOutput(248, 0, 30, 46)
  FillArea(277, 9, $00FF00, $00FF00)
  UnclipOutput()
  
  StopDrawing()
EndIf

Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow

[nicoh]

This works:

Code: Select all

  ;A
  ClipOutput(248, 100, 30, 54)
  FillArea(277, 110, $FF0000, $FF0000)
  UnclipOutput()
  
  ;B
  ClipOutput(248, 0, 30, 46)
  FillArea(277, 9, $00FF00, $00FF00)
  UnclipOutput()

But when swapping, it crashes.

Code: Select all

  ;B
  ClipOutput(248, 0, 30, 46)
  FillArea(277, 9, $00FF00, $00FF00)
  UnclipOutput()
  
  ;A
  ClipOutput(248, 100, 30, 54)
  FillArea(277, 110, $FF0000, $FF0000)
  UnclipOutput()

I don't get it, sorry.

[Mijikai]

That looks like a bug , FillArea() seems not to be correctly checked against the clipping rect.

[nicoh]

That looks like a bug , FillArea() seems not to be correctly checked against the clipping rect.

So someone could move this post back to "bug reports" please?

Edit: Created new bug report: https://www.purebasic.fr/english/viewtopic.php?t=79568