From f0367ee72d594afa6caaabe42feccf421f6d637c Mon Sep 17 00:00:00 2001
From: Thomas Friedel <tomee6@gmail.com>
Date: Wed, 4 Dec 2019 12:13:09 +0100
Subject: [PATCH] GetImageData bugfix

---
 backend/goglbackend/imagedata.go    | 15 ++++++++++-----
 backend/xmobilebackend/gen/gen.go   |  4 ++++
 backend/xmobilebackend/imagedata.go | 15 ++++++++++-----
 backend/xmobilebackend/images.go    |  2 +-
 4 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/backend/goglbackend/imagedata.go b/backend/goglbackend/imagedata.go
index d3bf9bb..a5161a0 100644
--- a/backend/goglbackend/imagedata.go
+++ b/backend/goglbackend/imagedata.go
@@ -26,14 +26,19 @@ func (b *GoGLBackend) GetImageData(x, y, w, h int) *image.RGBA {
 	if h > b.h {
 		h = b.h
 	}
-	if len(b.imageBuf) < w*h*3 {
-		b.imageBuf = make([]byte, w*h*3)
-	}
 
-	gl.ReadPixels(int32(x), int32(y), int32(w), int32(h), gl.RGB, gl.UNSIGNED_BYTE, gl.Ptr(&b.imageBuf[0]))
+	var vp [4]int32
+	gl.GetIntegerv(gl.VIEWPORT, &vp[0])
+
+	size := int(vp[2] * vp[3] * 3)
+	if len(b.imageBuf) < size {
+		b.imageBuf = make([]byte, size)
+	}
+	gl.ReadPixels(vp[0], vp[1], vp[2], vp[3], gl.RGB, gl.UNSIGNED_BYTE, gl.Ptr(&b.imageBuf[0]))
+
 	rgba := image.NewRGBA(image.Rect(x, y, x+w, y+h))
-	bp := 0
 	for cy := y; cy < y+h; cy++ {
+		bp := (int(vp[3])-h+cy)*int(vp[2])*3 + x*3
 		for cx := x; cx < x+w; cx++ {
 			rgba.SetRGBA(cx, y+h-1-cy, color.RGBA{R: b.imageBuf[bp], G: b.imageBuf[bp+1], B: b.imageBuf[bp+2], A: 255})
 			bp += 3
diff --git a/backend/xmobilebackend/gen/gen.go b/backend/xmobilebackend/gen/gen.go
index 5362b39..303e3e9 100644
--- a/backend/xmobilebackend/gen/gen.go
+++ b/backend/xmobilebackend/gen/gen.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"io/ioutil"
 	"log"
 	"os"
@@ -212,6 +213,8 @@ func rewrite(filename, src string) (string, string) {
 				params[i] = param[6 : len(param)-1]
 			} else if strings.HasPrefix(param, "gl.Ptr(") {
 				params[i] = param[8:len(param)-2] + ":]"
+			} else if len(param) >= 5 && param[:3] == "vp[" {
+				params[i] = fmt.Sprintf("int(%s)", param)
 			}
 		}
 		return "b.glctx.ReadPixels(" + params[6] + ", " + strings.Join(params[:len(params)-1], ", ") + ")"
@@ -239,6 +242,7 @@ func rewrite(filename, src string) (string, string) {
 	src = rewriteCalls(src, "loadShader", func(params []string) string {
 		return "loadShader(b, " + strings.Join(params, ", ") + ")"
 	})
+	src = strings.ReplaceAll(src, "if tex == 0 {", "if tex.Value == 0 {")
 
 	if filename == "gogl.go" {
 		filename = "xmobile.go"
diff --git a/backend/xmobilebackend/imagedata.go b/backend/xmobilebackend/imagedata.go
index 86bd625..a119b5a 100755
--- a/backend/xmobilebackend/imagedata.go
+++ b/backend/xmobilebackend/imagedata.go
@@ -26,14 +26,19 @@ func (b *XMobileBackend) GetImageData(x, y, w, h int) *image.RGBA {
 	if h > b.h {
 		h = b.h
 	}
-	if len(b.imageBuf) < w*h*3 {
-		b.imageBuf = make([]byte, w*h*3)
-	}
 
-	b.glctx.ReadPixels(b.imageBuf[0:], x, y, w, h, gl.RGB, gl.UNSIGNED_BYTE)
+	var vp [4]int32
+	b.glctx.GetIntegerv(vp[:], gl.VIEWPORT)
+
+	size := int(vp[2] * vp[3] * 3)
+	if len(b.imageBuf) < size {
+		b.imageBuf = make([]byte, size)
+	}
+	b.glctx.ReadPixels(b.imageBuf[0:], int(vp[0]), int(vp[1]), int(vp[2]), int(vp[3]), gl.RGB, gl.UNSIGNED_BYTE)
+
 	rgba := image.NewRGBA(image.Rect(x, y, x+w, y+h))
-	bp := 0
 	for cy := y; cy < y+h; cy++ {
+		bp := (int(vp[3])-h+cy)*int(vp[2])*3 + x*3
 		for cx := x; cx < x+w; cx++ {
 			rgba.SetRGBA(cx, y+h-1-cy, color.RGBA{R: b.imageBuf[bp], G: b.imageBuf[bp+1], B: b.imageBuf[bp+2], A: 255})
 			bp += 3
diff --git a/backend/xmobilebackend/images.go b/backend/xmobilebackend/images.go
index 4c01c5a..41d2751 100755
--- a/backend/xmobilebackend/images.go
+++ b/backend/xmobilebackend/images.go
@@ -23,7 +23,7 @@ func (b *XMobileBackend) LoadImage(src image.Image) (backendbase.Image, error) {
 
 	var tex gl.Texture
 	tex = b.glctx.CreateTexture()
-	if tex == 0 {
+	if tex.Value == 0 {
 		return nil, errors.New("glGenTextures failed")
 	}