graphicsdriver/opengl: Refactoring: Remove framebuffer.projectionMatrix

internal/graphicsdriver/opengl/framebuffer.go

@@ -16,11 +16,10 @@ package opengl
 
 // framebuffer is a wrapper of OpenGL's framebuffer.
 type framebuffer struct {
-	driver    *Driver
-	native    framebufferNative
-	proMatrix []float32
-	width     int
-	height    int
+	driver *Driver
+	native framebufferNative
+	width  int
+	height int
 }
 
 // newFramebufferFromTexture creates a framebuffer from the given texture.
@@ -45,19 +44,6 @@ func newScreenFramebuffer(context *context, width, height int) *framebuffer {
 	}
 }
 
-// projectionMatrix returns a projection matrix of the framebuffer.
-//
-// A projection matrix converts the coodinates on the framebuffer
-// (0, 0) - (viewport width, viewport height)
-// to the normalized device coodinates (-1, -1) - (1, 1) with adjustment.
-func (f *framebuffer) projectionMatrix() []float32 {
-	if f.proMatrix != nil {
-		return f.proMatrix
-	}
-	f.proMatrix = orthoProjectionMatrix(0, f.width, 0, f.height)
-	return f.proMatrix
-}
-
 func (f *framebuffer) delete(context *context) {
 	if f.native != context.getScreenFramebuffer() {
 		context.deleteFramebuffer(f.native)

internal/graphicsdriver/opengl/image.go

@@ -63,13 +63,6 @@ func (i *Image) Pixels() ([]byte, error) {
 	return p, nil
 }
 
-func (i *Image) projectionMatrix() []float32 {
-	if i.framebuffer == nil {
-		panic("not reached")
-	}
-	return i.framebuffer.projectionMatrix()
-}
-
 func (i *Image) ensureFramebuffer() error {
 	if i.framebuffer != nil {
 		return nil

internal/graphicsdriver/opengl/matrix.go

@@ -1,32 +0,0 @@
-// Copyright 2018 The Ebiten Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package opengl
-
-// orthoProjectionMatrix returns an orthogonal projection matrix for OpenGL.
-//
-// The matrix converts the coodinates (left, bottom) - (right, top) to the normalized device coodinates (-1, -1) - (1, 1).
-func orthoProjectionMatrix(left, right, bottom, top int) []float32 {
-	e11 := 2 / float32(right-left)
-	e22 := 2 / float32(top-bottom)
-	e14 := -1 * float32(right+left) / float32(right-left)
-	e24 := -1 * float32(top+bottom) / float32(top-bottom)
-
-	return []float32{
-		e11, 0, 0, 0,
-		0, e22, 0, 0,
-		0, 0, 1, 0,
-		e14, e24, 0, 1,
-	}
-}

internal/graphicsdriver/opengl/program.go

@@ -124,7 +124,7 @@ type openGLState struct {
 	programScreen program
 
 	lastProgram                program
-	lastProjectionMatrix       []float32
+	lastViewportSize           []float32
 	lastColorMatrix            []float32
 	lastColorMatrixTranslation []float32
 	lastSourceWidth            int
@@ -151,7 +151,7 @@ func (s *openGLState) reset(context *context) error {
 	}
 
 	s.lastProgram = zeroProgram
-	s.lastProjectionMatrix = nil
+	s.lastViewportSize = nil
 	s.lastColorMatrix = nil
 	s.lastColorMatrixTranslation = nil
 	s.lastSourceWidth = 0
@@ -266,7 +266,10 @@ func (d *Driver) useProgram(mode graphics.CompositeMode, colorM *affine.ColorM,
 	if err := destination.setViewport(); err != nil {
 		return err
 	}
-	proj := destination.projectionMatrix()
+	viewportSize := []float32{
+		float32(destination.framebuffer.width),
+		float32(destination.framebuffer.height),
+	}
 	dstW := destination.width
 	srcW, srcH := source.width, source.height
 
@@ -298,21 +301,19 @@ func (d *Driver) useProgram(mode graphics.CompositeMode, colorM *affine.ColorM,
 		}
 
 		d.state.lastProgram = program
-		d.state.lastProjectionMatrix = nil
+		d.state.lastViewportSize = nil
 		d.state.lastColorMatrix = nil
 		d.state.lastColorMatrixTranslation = nil
 		d.state.lastSourceWidth = 0
 		d.state.lastSourceHeight = 0
 	}
 
-	if !areSameFloat32Array(d.state.lastProjectionMatrix, proj) {
-		d.context.uniformFloats(program, "projection_matrix", proj)
-		if d.state.lastProjectionMatrix == nil {
-			d.state.lastProjectionMatrix = make([]float32, 16)
+	if !areSameFloat32Array(d.state.lastViewportSize, viewportSize) {
+		d.context.uniformFloats(program, "viewport_size", viewportSize)
+		if d.state.lastViewportSize == nil {
+			d.state.lastViewportSize = make([]float32, 2)
 		}
-		// (*framebuffer).projectionMatrix is always same for the same framebuffer.
-		// It's OK to hold the reference without copying.
-		d.state.lastProjectionMatrix = proj
+		d.state.lastViewportSize = viewportSize
 	}
 
 	esBody, esTranslate := colorM.UnsafeElements()

internal/graphicsdriver/opengl/shader.go

@@ -47,7 +47,7 @@ func shaderStr(id shaderID) string {
 
 const (
 	shaderStrVertex = `
-uniform mat4 projection_matrix;
+uniform vec2 viewport_size;
 attribute vec4 vertex;
 attribute vec4 tex_coord;
 attribute vec4 color_scale;
@@ -66,6 +66,13 @@ void main(void) {
     varying_tex_coord_max = vec2(1, 1);
   }
   varying_color_scale = color_scale;
+
+  mat4 projection_matrix = mat4(
+    vec4(2.0 / viewport_size.x, 0, 0, 0),
+    vec4(0, 2.0 / viewport_size.y, 0, 0),
+    vec4(0, 0, 1, 0),
+    vec4(-1, -1, 0, 1)
+  );
   gl_Position = projection_matrix * vertex;
 }
 `