internal/graphicsdriver/opengl: refactoring: rename variables

A framebuffer's width and height are unclear. Rename them to
viewportWidth and viewportHeight.

internal/graphicsdriver/opengl/context.go

@@ -141,14 +141,14 @@ func (c *context) bindFramebuffer(f framebufferNative) {
 
 func (c *context) setViewport(f *framebuffer) {
 	c.bindFramebuffer(f.native)
-	if c.lastViewportWidth == f.width && c.lastViewportHeight == f.height {
+	if c.lastViewportWidth == f.viewportWidth && c.lastViewportHeight == f.viewportHeight {
 		return
 	}
 
 	// On some environments, viewport size must be within the framebuffer size.
 	// e.g. Edge (#71), Chrome on GPD Pocket (#420), macOS Mojave (#691).
 	// Use the same size of the framebuffer here.
-	c.ctx.Viewport(0, 0, int32(f.width), int32(f.height))
+	c.ctx.Viewport(0, 0, int32(f.viewportWidth), int32(f.viewportHeight))
 
 	// glViewport must be called at least at every frame on iOS.
 	// As the screen framebuffer is the last render target, next SetViewport should be
@@ -157,16 +157,16 @@ func (c *context) setViewport(f *framebuffer) {
 		c.lastViewportWidth = 0
 		c.lastViewportHeight = 0
 	} else {
-		c.lastViewportWidth = f.width
-		c.lastViewportHeight = f.height
+		c.lastViewportWidth = f.viewportWidth
+		c.lastViewportHeight = f.viewportHeight
 	}
 }
 
 func (c *context) newScreenFramebuffer(width, height int) *framebuffer {
 	return &framebuffer{
-		native: c.screenFramebuffer,
-		width:  width,
-		height: height,
+		native:         c.screenFramebuffer,
+		viewportWidth:  width,
+		viewportHeight: height,
 	}
 }
 
@@ -346,9 +346,9 @@ func (c *context) newFramebuffer(texture textureNative, width, height int) (*fra
 		return nil, fmt.Errorf("opengl: creating framebuffer failed: unknown error")
 	}
 	return &framebuffer{
-		native: framebufferNative(f),
-		width:  width,
-		height: height,
+		native:         framebufferNative(f),
+		viewportWidth:  width,
+		viewportHeight: height,
 	}, nil
 }
 

internal/graphicsdriver/opengl/image.go

@@ -37,10 +37,9 @@ type Image struct {
 
 // framebuffer is a wrapper of OpenGL's framebuffer.
 type framebuffer struct {
-	graphics *Graphics
-	native   framebufferNative
-	width    int
-	height   int
+	native         framebufferNative
+	viewportWidth  int
+	viewportHeight int
 }
 
 func (i *Image) ID() graphicsdriver.ImageID {
@@ -81,7 +80,7 @@ func (i *Image) ReadPixels(args []graphicsdriver.PixelsArgs) error {
 	return nil
 }
 
-func (i *Image) framebufferSize() (int, int) {
+func (i *Image) viewportSize() (int, int) {
 	if i.screen {
 		// The (default) framebuffer size can't be converted to a power of 2.
 		// On browsers, i.width and i.height are used as viewport size and
@@ -96,11 +95,12 @@ func (i *Image) ensureFramebuffer() error {
 		return nil
 	}
 
-	w, h := i.framebufferSize()
+	w, h := i.viewportSize()
 	if i.screen {
 		i.framebuffer = i.graphics.context.newScreenFramebuffer(w, h)
 		return nil
 	}
+
 	f, err := i.graphics.context.newFramebuffer(i.texture, w, h)
 	if err != nil {
 		return err
@@ -118,7 +118,7 @@ func (i *Image) ensureStencilBuffer() error {
 		return err
 	}
 
-	r, err := i.graphics.context.newRenderbuffer(i.framebufferSize())
+	r, err := i.graphics.context.newRenderbuffer(i.viewportSize())
 	if err != nil {
 		return err
 	}