opengl: Refactoring: Remove ResetViewportSize

internal/graphicscommand/command.go

@@ -146,13 +146,6 @@ func (q *commandQueue) Flush() {
 		return
 	}
 
-	// glViewport must be called at least at every frame on iOS.
-	// This is introduced at https://github.com/hajimehoshi/ebiten/commit/e9de66aca2007a679de4ba11ea14ef061dca2f6e.
-	// At that time viewport sizes were always same so it was needed to force to call
-	// glViewport, but now viewport sizes can change and apps can work without this. This is
-	// needed only when the screen framebuffer size and the first framebuffer size are same,
-	// probably.
-	opengl.GetContext().ResetViewportSize()
 	es := q.indices
 	vs := q.vertices
 	if recordLog() {

internal/opengl/context.go

@@ -100,8 +100,16 @@ func (c *Context) SetViewport(f Framebuffer, width, height int) {
 	c.bindFramebuffer(f)
 	if c.lastViewportWidth != width || c.lastViewportHeight != height {
 		c.setViewportImpl(width, height)
-		c.lastViewportWidth = width
-		c.lastViewportHeight = height
+		// glViewport must be called at least at every frame on iOS.
+		// As the screen framebuffer is the last render target, next SetViewport should be
+		// the first call at a frame.
+		if f == c.screenFramebuffer {
+			c.lastViewportWidth = 0
+			c.lastViewportHeight = 0
+		} else {
+			c.lastViewportWidth = width
+			c.lastViewportHeight = height
+		}
 	}
 }
 
@@ -109,11 +117,6 @@ func (c *Context) ScreenFramebuffer() Framebuffer {
 	return c.screenFramebuffer
 }
 
-func (c *Context) ResetViewportSize() {
-	c.lastViewportWidth = 0
-	c.lastViewportHeight = 0
-}
-
 func (c *Context) MaxTextureSize() int {
 	if c.maxTextureSize == 0 {
 		c.maxTextureSize = c.maxTextureSizeImpl()