From c76893c9aa0b9be7955516ba8da6469eb96608f5 Mon Sep 17 00:00:00 2001
From: Andy Williams <andy@andy.xyz>
Date: Mon, 18 Sep 2023 21:28:29 +0100
Subject: [PATCH] Move Circle to GL shader

---
 internal/painter/gl/draw.go | 81 +++++++++++++++++++++++++++++++++++--
 1 file changed, 77 insertions(+), 4 deletions(-)

diff --git a/internal/painter/gl/draw.go b/internal/painter/gl/draw.go
index 96e1e5bd7e..807c8f6b02 100644
--- a/internal/painter/gl/draw.go
+++ b/internal/painter/gl/draw.go
@@ -29,6 +29,64 @@ func (p *painter) defineVertexArray(prog Program, name string, size, stride, off
 func (p *painter) drawCircle(circle *canvas.Circle, pos fyne.Position, frame fyne.Size) {
 	p.drawTextureWithDetails(circle, p.newGlCircleTexture, pos, circle.Size(), frame, canvas.ImageFillStretch,
 		1.0, paint.VectorPad(circle))
+
+	radius := circle.Size().Width / 2
+	if circle.Size().Height < circle.Size().Width {
+		radius = circle.Size().Height / 2
+	}
+	program := p.roundRectangleProgram
+
+	// Vertex: BEG
+	bounds, points := p.vecSquareCoords(pos, circle, frame)
+	p.ctx.UseProgram(program)
+	vbo := p.createBuffer(points)
+	p.defineVertexArray(program, "vert", 2, 4, 0)
+	p.defineVertexArray(program, "normal", 2, 4, 2)
+
+	p.ctx.BlendFunc(srcAlpha, oneMinusSrcAlpha)
+	p.logError()
+	// Vertex: END
+
+	// Fragment: BEG
+	frameSizeUniform := p.ctx.GetUniformLocation(program, "frame_size")
+	frameWidthScaled, frameHeightScaled := p.scaleFrameSize(frame)
+	p.ctx.Uniform2f(frameSizeUniform, frameWidthScaled, frameHeightScaled)
+
+	rectCoordsUniform := p.ctx.GetUniformLocation(program, "rect_coords")
+	x1Scaled, x2Scaled, y1Scaled, y2Scaled := p.scaleRectCoords(bounds[0], bounds[2], bounds[1], bounds[3])
+	p.ctx.Uniform4f(rectCoordsUniform, x1Scaled, x2Scaled, y1Scaled, y2Scaled)
+
+	strokeWidthScaled := roundToPixel(circle.StrokeWidth*p.pixScale, 1.0)
+	strokeUniform := p.ctx.GetUniformLocation(program, "stroke_width_half")
+	p.ctx.Uniform1f(strokeUniform, strokeWidthScaled*0.5)
+
+	rectSizeUniform := p.ctx.GetUniformLocation(program, "rect_size_half")
+	rectSizeWidthScaled := x2Scaled - x1Scaled - strokeWidthScaled
+	rectSizeHeightScaled := y2Scaled - y1Scaled - strokeWidthScaled
+	p.ctx.Uniform2f(rectSizeUniform, rectSizeWidthScaled*0.5, rectSizeHeightScaled*0.5)
+
+	radiusUniform := p.ctx.GetUniformLocation(program, "radius")
+	radiusScaled := roundToPixel(radius*p.pixScale, 1.0)
+	p.ctx.Uniform1f(radiusUniform, radiusScaled)
+
+	var r, g, b, a float32
+	fillColorUniform := p.ctx.GetUniformLocation(program, "fill_color")
+	r, g, b, a = getFragmentColor(circle.FillColor)
+	p.ctx.Uniform4f(fillColorUniform, r, g, b, a)
+
+	strokeColorUniform := p.ctx.GetUniformLocation(program, "stroke_color")
+	strokeColor := circle.StrokeColor
+	if strokeColor == nil {
+		strokeColor = color.Transparent
+	}
+	r, g, b, a = getFragmentColor(strokeColor)
+	p.ctx.Uniform4f(strokeColorUniform, r, g, b, a)
+	p.logError()
+	// Fragment: END
+
+	p.ctx.DrawArrays(triangleStrip, 0, 4)
+	p.logError()
+	p.freeBuffer(vbo)
 }
 
 func (p *painter) drawGradient(o fyne.CanvasObject, texCreator func(fyne.CanvasObject) Texture, pos fyne.Position, frame fyne.Size) {
@@ -338,15 +396,19 @@ func rectInnerCoords(size fyne.Size, pos fyne.Position, fill canvas.ImageFill, a
 }
 
 func (p *painter) vecRectCoords(pos fyne.Position, rect *canvas.Rectangle, frame fyne.Size) ([4]float32, []float32) {
+	return p.vecRectCoordsWithPad(pos, rect, frame, 0, 0)
+}
+
+func (p *painter) vecRectCoordsWithPad(pos fyne.Position, rect fyne.CanvasObject, frame fyne.Size, xPad, yPad float32) ([4]float32, []float32) {
 	size := rect.Size()
 	pos1 := rect.Position()
 
-	xPosDiff := pos.X - pos1.X
-	yPosDiff := pos.Y - pos1.Y
+	xPosDiff := pos.X - pos1.X + xPad
+	yPosDiff := pos.Y - pos1.Y + yPad
 	pos1.X = roundToPixel(pos1.X+xPosDiff, p.pixScale)
 	pos1.Y = roundToPixel(pos1.Y+yPosDiff, p.pixScale)
-	size.Width = roundToPixel(size.Width, p.pixScale)
-	size.Height = roundToPixel(size.Height, p.pixScale)
+	size.Width = roundToPixel(size.Width-2*xPad, p.pixScale)
+	size.Height = roundToPixel(size.Height-2*yPad, p.pixScale)
 
 	x1Pos := pos1.X
 	x1Norm := -1 + x1Pos*2/frame.Width
@@ -367,6 +429,17 @@ func (p *painter) vecRectCoords(pos fyne.Position, rect *canvas.Rectangle, frame
 	return [4]float32{x1Pos, y1Pos, x2Pos, y2Pos}, coords
 }
 
+func (p *painter) vecSquareCoords(pos fyne.Position, rect fyne.CanvasObject, frame fyne.Size) ([4]float32, []float32) {
+	xPad, yPad := float32(0), float32(0)
+	if rect.Size().Width > rect.Size().Height {
+		xPad = (rect.Size().Width - rect.Size().Height) / 2
+	} else {
+		yPad = (rect.Size().Height - rect.Size().Width) / 2
+	}
+
+	return p.vecRectCoordsWithPad(pos, rect, frame, xPad, yPad)
+}
+
 func roundToPixel(v float32, pixScale float32) float32 {
 	if pixScale == 1.0 {
 		return float32(math.Round(float64(v)))