From 72c02fc3981871bf6a02a32342fb7a72fe3a5aa2 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 9 Sep 2017 19:24:56 +0900
Subject: [PATCH] graphics: Bug fix: viewport size must be within the
 framebuffer size

This fixes #71 and #420
---
 internal/graphics/framebuffer.go | 6 +++++-
 internal/web/js.go               | 9 ++++-----
 internal/web/notjs.go            | 4 ++--
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/internal/graphics/framebuffer.go b/internal/graphics/framebuffer.go
index 7c56b6df2..16cfa04e0 100644
--- a/internal/graphics/framebuffer.go
+++ b/internal/graphics/framebuffer.go
@@ -58,9 +58,13 @@ func newFramebufferFromTexture(texture *texture, width, height int) (*framebuffe
 const defaultViewportSize = 4096
 
 func (f *framebuffer) viewportSize() (int, int) {
-	if web.IsEdgeBrowser() {
+	// On some browsers, viewport size must be within the framebuffer size.
+	// e.g. Edge (#71), Chrome on GPD Pocket (#420)
+	if web.IsBrowser() {
 		return f.width, f.height
 	}
+
+	// If possible, always use the same viewport size to reduce draw calls.
 	return defaultViewportSize, defaultViewportSize
 }
 
diff --git a/internal/web/js.go b/internal/web/js.go
index 0e323f0fb..3ae242c57 100644
--- a/internal/web/js.go
+++ b/internal/web/js.go
@@ -22,6 +22,10 @@ import (
 	"github.com/gopherjs/gopherjs/js"
 )
 
+func IsBrowser() bool {
+	return true
+}
+
 func isIOS() bool {
 	ua := js.Global.Get("navigator").Get("userAgent").String()
 	if !strings.Contains(ua, "iPhone") {
@@ -44,8 +48,3 @@ func isAndroidChrome() bool {
 func IsMobileBrowser() bool {
 	return isIOS() || isAndroidChrome()
 }
-
-func IsEdgeBrowser() bool {
-	ua := js.Global.Get("navigator").Get("userAgent").String()
-	return strings.Contains(ua, "Edge")
-}
diff --git a/internal/web/notjs.go b/internal/web/notjs.go
index 3250b9ce0..bdd483258 100644
--- a/internal/web/notjs.go
+++ b/internal/web/notjs.go
@@ -16,10 +16,10 @@
 
 package web
 
-func IsMobileBrowser() bool {
+func IsBrowser() bool {
 	return false
 }
 
-func IsEdgeBrowser() bool {
+func IsMobileBrowser() bool {
 	return false
 }