From a637ac256da54e31fc6a934c0d0394dea356640c Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Fri, 28 Feb 2020 18:27:13 -0800
Subject: [PATCH] Qt: Fix OpenGL 2.1 support (fixes #1678)

---
 CHANGES                     |  1 +
 src/platform/opengl/gles2.c | 13 +++++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/CHANGES b/CHANGES
index 670995c70..1454aeb76 100644
--- a/CHANGES
+++ b/CHANGES
@@ -22,6 +22,7 @@ Other fixes:
  - GBA: Reject incorrectly sized BIOSes
  - Debugger: Don't skip undefined instructions when debugger attached
  - Qt: Force OpenGL paint engine creation thread (fixes mgba.io/i/1642)
+ - Qt: Fix OpenGL 2.1 support (fixes mgba.io/i/1678)
 Misc:
  - FFmpeg: Add looping option for GIF/APNG
  - Qt: Renderer can be changed while a game is running
diff --git a/src/platform/opengl/gles2.c b/src/platform/opengl/gles2.c
index 25d7edb00..fbb0fa601 100644
--- a/src/platform/opengl/gles2.c
+++ b/src/platform/opengl/gles2.c
@@ -21,6 +21,9 @@ static const GLchar* const _gles2Header =
 	"#version 100\n"
 	"precision mediump float;\n";
 
+static const GLchar* const _gl2Header =
+	"#version 120\n";
+
 static const GLchar* const _gl32VHeader =
 	"#version 150 core\n"
 	"#define attribute in\n"
@@ -462,10 +465,12 @@ void mGLES2ShaderInit(struct mGLES2Shader* shader, const char* vs, const char* f
 	shader->fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
 	const GLchar* shaderBuffer[2];
 	const GLubyte* version = glGetString(GL_VERSION);
-	if (strncmp((const char*) version, "OpenGL ES ", strlen("OpenGL ES "))) {
-		shaderBuffer[0] = _gl32VHeader;
-	} else {
+	if (strncmp((const char*) version, "OpenGL ES ", strlen("OpenGL ES ")) == 0) {
 		shaderBuffer[0] = _gles2Header;
+	} else if (version[0] == '2') {
+		shaderBuffer[0] = _gl2Header;
+	} else {
+		shaderBuffer[0] = _gl32VHeader;
 	}
 	if (vs) {
 		shaderBuffer[1] = vs;
@@ -474,7 +479,7 @@ void mGLES2ShaderInit(struct mGLES2Shader* shader, const char* vs, const char* f
 	}
 	glShaderSource(shader->vertexShader, 2, shaderBuffer, 0);
 
-	if (strncmp((const char*) version, "OpenGL ES ", strlen("OpenGL ES "))) {
+	if (shaderBuffer[0] == _gl32VHeader) {
 		shaderBuffer[0] = _gl32FHeader;
 	}
 	if (fs) {