Improve font rendering performance, eliminate excessive memory usage

glfont/font.go

@@ -17,17 +17,19 @@ const DPI = 72
 
 // A Font allows rendering of text to an OpenGL context.
 type Font struct {
-	characters  map[rune]*character
-	vao         uint32
-	vbo         uint32
-	program     uint32
-	texture     uint32 // Holds the glyph texture id.
-	color       color
-	ttf         *truetype.Font
-	ttfFace     font.Face
-	scale       float32
-	linePadding float32
-	lineHeight  float32
+	characters                map[rune]*character
+	vao                       uint32
+	vbo                       uint32
+	program                   uint32
+	uniformLocationResolution int32
+	uniformLocationTextColor  int32
+	texture                   uint32 // Holds the glyph texture id.
+	color                     color
+	ttf                       *truetype.Font
+	ttfFace                   font.Face
+	scale                     float32
+	linePadding               float32
+	lineHeight                float32
 }
 
 type color struct {
@@ -46,15 +48,14 @@ func LoadFont(reader io.Reader, scale float32, windowWidth int, windowHeight int
 		panic(err)
 	}
 
-	// Activate corresponding render state
-	gl.UseProgram(program)
+	font, err := LoadTrueTypeFont(program, reader, scale)
+	if err != nil {
+		return nil, err
+	}
 
-	//set screen resolution
-	resUniform := gl.GetUniformLocation(program, gl.Str("resolution\x00"))
-	gl.Uniform2f(resUniform, float32(windowWidth), float32(windowHeight))
-	gl.UseProgram(0)
+	font.UpdateResolution(windowWidth, windowHeight)
 
-	return LoadTrueTypeFont(program, reader, scale)
+	return font, nil
 }
 
 func (f *Font) Free() {
@@ -82,10 +83,8 @@ func (f *Font) SetColor(red float32, green float32, blue float32, alpha float32)
 
 func (f *Font) UpdateResolution(windowWidth int, windowHeight int) {
 	gl.UseProgram(f.program)
-	resUniform := gl.GetUniformLocation(f.program, gl.Str("resolution\x00"))
-	gl.Uniform2f(resUniform, float32(windowWidth), float32(windowHeight))
+	gl.Uniform2f(f.uniformLocationResolution, float32(windowWidth), float32(windowHeight))
 	gl.UseProgram(0)
-	//f.characters = map[rune]*character{}
 }
 
 func (f *Font) LineHeight() float32 {
@@ -112,13 +111,11 @@ func (f *Font) Print(x, y float32, text string) error {
 	// Activate corresponding render state
 	gl.UseProgram(f.program)
 	//set text color
-	gl.Uniform4f(gl.GetUniformLocation(f.program, gl.Str("textColor\x00")), f.color.r, f.color.g, f.color.b, f.color.a)
-	//set screen resolution
-	//resUniform := gl.GetUniformLocation(f.program, gl.Str("resolution\x00"))
-	//gl.Uniform2f(resUniform, float32(2560), float32(1440))
+	gl.Uniform4f(f.uniformLocationTextColor, f.color.r, f.color.g, f.color.b, f.color.a)
 
 	gl.ActiveTexture(gl.TEXTURE0)
 	gl.BindVertexArray(f.vao)
+	gl.BindBuffer(gl.ARRAY_BUFFER, f.vbo)
 
 	// Iterate through all characters in string
 	for i := range indices {
@@ -145,7 +142,7 @@ func (f *Font) Print(x, y float32, text string) error {
 		var y2 = ypos + h
 
 		//setup quad array
-		var vertices = []float32{
+		var vertices = [...]float32{
 			//  X, Y, Z, U, V
 			// Front
 			x1, y1, 0.0, 0.0,
@@ -153,25 +150,24 @@ func (f *Font) Print(x, y float32, text string) error {
 			x1, y2, 0.0, 1.0,
 			x1, y2, 0.0, 1.0,
 			x2, y1, 1.0, 0.0,
-			x2, y2, 1.0, 1.0}
+			x2, y2, 1.0, 1.0,
+		}
 
 		// Render glyph texture over quad
 		gl.BindTexture(gl.TEXTURE_2D, ch.textureID)
-		// Update content of VBO memory
-		gl.BindBuffer(gl.ARRAY_BUFFER, f.vbo)
 
-		//BufferSubData(target Enum, offset int, data []byte)
-		gl.BufferSubData(gl.ARRAY_BUFFER, 0, len(vertices)*4, gl.Ptr(vertices)) // Be sure to use glBufferSubData and not glBufferData
+		// Update content of VBO memory
+		gl.NamedBufferSubData(f.vbo, 0, len(vertices)*4, gl.Ptr(&vertices[0])) // Be sure to use glBufferSubData and not glBufferData
+
 		// Render quad
 		gl.DrawArrays(gl.TRIANGLES, 0, 24)
 
-		gl.BindBuffer(gl.ARRAY_BUFFER, 0)
 		// Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
 		x += float32((ch.advance >> 6)) // Bitshift by 6 to get value in pixels (2^6 = 64 (divide amount of 1/64th pixels by 64 to get amount of pixels))
-
 	}
 
 	//clear opengl textures and programs
+	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
 	gl.BindVertexArray(0)
 	gl.BindTexture(gl.TEXTURE_2D, 0)
 	gl.UseProgram(0)
@@ -308,6 +304,7 @@ func (f *Font) GetRune(r rune) (*character, error) {
 	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
 	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, int32(rgba.Rect.Dx()), int32(rgba.Rect.Dy()), 0,
 		gl.RGBA, gl.UNSIGNED_BYTE, gl.Ptr(rgba.Pix))
+	gl.BindTexture(gl.TEXTURE_2D, 0)
 
 	char.textureID = texture
 

glfont/truetype.go

@@ -30,6 +30,9 @@ func LoadTrueTypeFont(program uint32, r io.Reader, scale float32) (*Font, error)
 	f.scale = scale
 	f.characters = map[rune]*character{}
 	f.program = program //set shader program
+	f.uniformLocationResolution = gl.GetUniformLocation(program, gl.Str("resolution\x00"))
+	f.uniformLocationTextColor = gl.GetUniformLocation(program, gl.Str("textColor\x00"))
+
 	// Read the truetype font.
 	f.ttf, err = truetype.Parse(data)
 	if err != nil {

gui/fonts.go

@@ -47,3 +47,7 @@ func (gui *GUI) loadFonts(actualWidth int, actualHeight int) error {
 
 	return nil
 }
+
+func (gui *GUI) updateFontsResolution(actualWidth int, actualHeight int) {
+	gui.fontMap.UpdateResolution(actualWidth, actualHeight)
+}

gui/gui.go

@@ -321,7 +321,7 @@ func (gui *GUI) resize(w *glfw.Window, width int, height int) {
 	}
 
 	gui.logger.Debugf("Updating font resolutions...")
-	gui.loadFonts(gui.width, gui.height)
+	gui.updateFontsResolution(gui.width, gui.height)
 
 	gui.logger.Debugf("Setting renderer area...")
 	gui.renderer.SetArea(0, 0, gui.width-vScrollbarWidth, gui.height)