internal/graphicscommand: remove the dependency on a graphics driver from compileShader

Updates #2035

internal/graphics/vertex.go

@@ -29,7 +29,8 @@ const (
 		1 + // the texture destination region's size
 		1 + // the offsets array of the second and the following images
 		1 + // the texture source region's origin
-		1 // the texture source region's size
+		1 + // the texture source region's size
+		1 // the projection matrix
 
 	TextureDestinationSizeUniformVariableIndex         = 0
 	TextureSourceSizesUniformVariableIndex             = 1
@@ -38,6 +39,7 @@ const (
 	TextureSourceOffsetsUniformVariableIndex           = 4
 	TextureSourceRegionOriginUniformVariableIndex      = 5
 	TextureSourceRegionSizeUniformVariableIndex        = 6
+	ProjectionMatrixUniformVariableIndex               = 7
 )
 
 const (

internal/graphicscommand/command.go

@@ -666,7 +666,7 @@ func (c *newShaderCommand) String() string {
 
 // Exec executes a newShaderCommand.
 func (c *newShaderCommand) Exec(graphicsDriver graphicsdriver.Graphics, indexOffset int) error {
-	ir, err := compileShader(graphicsDriver, c.src)
+	ir, err := compileShader(c.src)
 	if err != nil {
 		return err
 	}

internal/graphicscommand/shader.go

@@ -106,33 +106,16 @@ func imageSrc%[1]dAt(pos vec2) vec4 {
 	}
 }
 
-func compileShader(graphicsDriver graphicsdriver.Graphics, src []byte) (*shaderir.Program, error) {
+func compileShader(src []byte) (*shaderir.Program, error) {
 	var buf bytes.Buffer
 	buf.Write(src)
 	buf.WriteString(shaderSuffix)
-	if graphicsDriver.FramebufferYDirection() != graphicsDriver.NDCYDirection() {
-		buf.WriteString(`
+	buf.WriteString(`var __projectionMatrix mat4
+
 func __vertex(position vec2, texCoord vec2, color vec4) (vec4, vec2, vec4) {
-	return mat4(
-		2/__imageDstTextureSize.x, 0, 0, 0,
-		0, -2/__imageDstTextureSize.y, 0, 0,
-		0, 0, 1, 0,
-		-1, 1, 0, 1,
-	) * vec4(position, 0, 1), texCoord, color
+	return __projectionMatrix * vec4(position, 0, 1), texCoord, color
 }
 `)
-	} else {
-		buf.WriteString(`
-func __vertex(position vec2, texCoord vec2, color vec4) (vec4, vec2, vec4) {
-	return mat4(
-		2/__imageDstTextureSize.x, 0, 0, 0,
-		0, 2/__imageDstTextureSize.y, 0, 0,
-		0, 0, 1, 0,
-		-1, -1, 0, 1,
-	) * vec4(position, 0, 1), texCoord, color
-}
-`)
-	}
 
 	fs := token.NewFileSet()
 	f, err := parser.ParseFile(fs, "", buf.Bytes(), parser.AllErrors)

internal/graphicsdriver/directx/graphics_windows.go

@@ -1056,6 +1056,12 @@ func (g *Graphics) DrawTriangles(dstID graphicsdriver.ImageID, srcs [graphics.Sh
 		us[graphics.TextureSourceRegionOriginUniformVariableIndex] = usorigin
 		ussize := []float32{float32(srcRegion.Width), float32(srcRegion.Height)}
 		us[graphics.TextureSourceRegionSizeUniformVariableIndex] = ussize
+		us[graphics.ProjectionMatrixUniformVariableIndex] = []float32{
+			2 / float32(dw), 0, 0, 0,
+			0, -2 / float32(dh), 0, 0,
+			0, 0, 1, 0,
+			-1, 1, 0, 1,
+		}
 
 		for i, u := range uniforms {
 			us[graphics.PreservedUniformVariablesNum+i] = u

internal/graphicsdriver/metal/graphics_darwin.go

@@ -995,6 +995,13 @@ func (g *Graphics) DrawTriangles(dstID graphicsdriver.ImageID, srcIDs [graphics.
 		ussize := []float32{float32(srcRegion.Width), float32(srcRegion.Height)}
 		uniformVars[graphics.TextureSourceRegionSizeUniformVariableIndex] = ussize
 
+		uniformVars[graphics.ProjectionMatrixUniformVariableIndex] = []float32{
+			2 / float32(dw), 0, 0, 0,
+			0, -2 / float32(dh), 0, 0,
+			0, 0, 1, 0,
+			-1, 1, 0, 1,
+		}
+
 		// Set the additional uniform variables.
 		for i, v := range uniforms {
 			const offset = graphics.PreservedUniformVariablesNum

internal/graphicsdriver/opengl/graphics.go

@@ -320,6 +320,17 @@ func (g *Graphics) DrawTriangles(dstID graphicsdriver.ImageID, srcIDs [graphics.
 			g.uniformVars[idx].value = size
 			g.uniformVars[idx].typ = shader.ir.Uniforms[idx]
 		}
+		{
+			const idx = graphics.ProjectionMatrixUniformVariableIndex
+			g.uniformVars[idx].name = g.uniformVariableName(idx)
+			g.uniformVars[idx].value = []float32{
+				2 / float32(dw), 0, 0, 0,
+				0, 2 / float32(dh), 0, 0,
+				0, 0, 1, 0,
+				-1, -1, 0, 1,
+			}
+			g.uniformVars[idx].typ = shader.ir.Uniforms[idx]
+		}
 
 		for i, v := range uniforms {
 			const offset = graphics.PreservedUniformVariablesNum