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Improve scissor test implementation in Filler's Render method for accurate clipping. Refactored coordinate conversion and added comments for clarity on OpenGL rendering boundaries.

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mleku
2025-10-26 21:29:32 +00:00
parent ecf7cfd689
commit 964dba1262
1 changed files with 17 additions and 12 deletions
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29
pkg/widget/fill.go
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@@ -30,25 +30,30 @@ func (f *Filler) GetConstraints() Constraints {
// Render implements the Widget interface for Fill
func (f *Filler) Render(ctx *Context, box *Box) (usedSize Size, err error) {
// Set scissor test to clip to the box
// Convert from GL coordinates (bottom-left origin) to screen coordinates (top-left origin)
// Window height is ctx.WindowHeight, box Y is from top
scissorX := int32(box.Position.X)
scissorY := int32(float32(ctx.WindowHeight) - box.Position.Y - box.Size.Height)
scissorW := int32(box.Size.Width)
scissorH := int32(box.Size.Height)
gl.Scissor(scissorX, scissorY, scissorW, scissorH)
// Convert to OpenGL coordinates (bottom-left origin) from top-left origin
// Box Y is from top, convert to bottom-left
bottomY := float32(ctx.WindowHeight) - box.Position.Y - box.Size.Height
// Set the color
gl.Color4f(f.color[0], f.color[1], f.color[2], f.color[3])
// Create vertices for the quad
// Create vertices for the quad (exact pixel boundaries)
x1, y1 := box.Position.X, float32(ctx.WindowHeight)-box.Position.Y
x2, y2 := box.Position.X+box.Size.Width, float32(ctx.WindowHeight)-box.Position.Y
x3, y3 := box.Position.X+box.Size.Width, float32(ctx.WindowHeight)-box.Position.Y-box.Size.Height
x4, y4 := box.Position.X, float32(ctx.WindowHeight)-box.Position.Y-box.Size.Height
// Enable scissor test with proper boundaries to enforce clipping
// This prevents artifacts at the edges by ensuring rendering doesn't go beyond boundaries
gl.Scissor(
int32(box.Position.X),
int32(bottomY),
int32(box.Size.Width),
int32(box.Size.Height),
)
// Set the color
gl.Color4f(f.color[0], f.color[1], f.color[2], f.color[3])
// Draw using immediate mode
// The scissor test will clip these vertices to the exact boundaries
gl.Begin(gl.QUADS)
gl.Vertex2f(x1, y1)
gl.Vertex2f(x2, y2)