CanvasBuffer

CanvasBuffer

Command Index · BlitzPlus · Canvas

CanvasBuffer:Int32 canvas:Int32

Parameter	Mode	Type	Default	Description
canvas	In	Int32	required	Handle of a canvas made with CreateCanvas.

Returns: A buffer handle that works with SetBuffer, LockBuffer, ReadPixel and the other buffer commands.

Description

Gives the buffer that a canvas is drawn to. Make it the target with SetBuffer, draw with the usual 2D commands like Rect, Line and Text, and then call FlipCanvas to show the result. The buffer is as big as the canvas.

Differences

• The buffer has 32 bits of color (RGBA8) whatever depth Graphics has, and it is drawn to by the same renderer as the back buffer: Cls, the 2D commands, RenderWorld, CopyRect, ReadPixel and LockBuffer work in it the same way. When the canvas changes size (SetGadgetShape, or its layout following the window) the next CanvasBuffer gives a buffer of the new size, with what was drawn before gone, and keeps its handle as long as the size stays. The buffer is as big as the canvas is in the units of the program whatever the display scales the window by, see CreateWindow: on a display with a high density of pixels the picture is enlarged when the window is drawn.

Examples

Graphics 320, 240, 32, 2
win = CreateWindow("Canvas", 20, 20, 280, 190, Desktop(), 3)
cv  = CreateCanvas(10, 10, 250, 140, win)
SetBuffer CanvasBuffer(cv)
ClsColor 20, 30, 60
Cls
Color 255, 200, 0
Oval 20, 20, 100, 100, 1
Color 255, 255, 255
Text 135, 60, "Drawn on a canvas"
FlipCanvas cv
Repeat
Until WaitEvent() = $803

Media

Related Commands

CreateCanvas, DesktopBuffer, FlipCanvas

Command Index · BlitzPlus · Canvas