From 0dff3ef144c450d0ef0dbec0461afc8cc22223ba Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Thu, 6 May 2021 00:23:46 +0300
Subject: [PATCH] A flag to disable OpenGL, better and more stable handling of
 no-OpenGL mode

---
 SDL/gui.c    |  7 +++++++
 SDL/main.c   | 20 ++++++++++++++------
 SDL/shader.c |  4 ++++
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/SDL/gui.c b/SDL/gui.c
index b8e69cdd..ae39f7ea 100644
--- a/SDL/gui.c
+++ b/SDL/gui.c
@@ -676,6 +676,7 @@ static void cycle_border_mode_backwards(unsigned index)
     }
 }
 
+extern bool uses_gl(void);
 struct shader_name {
     const char *file_name;
     const char *display_name;
@@ -699,6 +700,7 @@ struct shader_name {
 
 static void cycle_filter(unsigned index)
 {
+    if (!uses_gl()) return;
     unsigned i = 0;
     for (; i < sizeof(shaders) / sizeof(shaders[0]); i++) {
         if (strcmp(shaders[i].file_name, configuration.filter) == 0) {
@@ -721,6 +723,7 @@ static void cycle_filter(unsigned index)
 
 static void cycle_filter_backwards(unsigned index)
 {
+    if (!uses_gl()) return;
     unsigned i = 0;
     for (; i < sizeof(shaders) / sizeof(shaders[0]); i++) {
         if (strcmp(shaders[i].file_name, configuration.filter) == 0) {
@@ -742,6 +745,7 @@ static void cycle_filter_backwards(unsigned index)
 }
 const char *current_filter_name(unsigned index)
 {
+    if (!uses_gl()) return "Requires OpenGL 3.2+";
     unsigned i = 0;
     for (; i < sizeof(shaders) / sizeof(shaders[0]); i++) {
         if (strcmp(shaders[i].file_name, configuration.filter) == 0) {
@@ -758,6 +762,7 @@ const char *current_filter_name(unsigned index)
 
 static void cycle_blending_mode(unsigned index)
 {
+        if (!uses_gl()) return;
     if (configuration.blending_mode == GB_FRAME_BLENDING_MODE_ACCURATE) {
         configuration.blending_mode = GB_FRAME_BLENDING_MODE_DISABLED;
     }
@@ -768,6 +773,7 @@ static void cycle_blending_mode(unsigned index)
 
 static void cycle_blending_mode_backwards(unsigned index)
 {
+    if (!uses_gl()) return;
     if (configuration.blending_mode == GB_FRAME_BLENDING_MODE_DISABLED) {
         configuration.blending_mode = GB_FRAME_BLENDING_MODE_ACCURATE;
     }
@@ -778,6 +784,7 @@ static void cycle_blending_mode_backwards(unsigned index)
 
 const char *blending_mode_string(unsigned index)
 {
+    if (!uses_gl()) return "Requires OpenGL 3.2+";
     return (const char *[]){"Disabled", "Simple", "Accurate"}
     [configuration.blending_mode];
 }
diff --git a/SDL/main.c b/SDL/main.c
index 29398b71..5afc6dea 100644
--- a/SDL/main.c
+++ b/SDL/main.c
@@ -25,8 +25,13 @@ static double clock_mutliplier = 1.0;
 
 static char *filename = NULL;
 static typeof(free) *free_function = NULL;
-static char *battery_save_path_ptr;
+static char *battery_save_path_ptr = NULL;
+static SDL_GLContext gl_context = NULL;
 
+bool uses_gl(void)
+{
+    return gl_context;
+}
 
 void set_filename(const char *new_filename, typeof(free) *new_free_function)
 {
@@ -637,9 +642,10 @@ int main(int argc, char **argv)
     fprintf(stderr, "SameBoy v" xstr(VERSION) "\n");
     
     bool fullscreen = get_arg_flag("--fullscreen", &argc, argv);
+    bool nogl = get_arg_flag("--nogl", &argc, argv);
 
     if (argc > 2) {
-        fprintf(stderr, "Usage: %s [--fullscreen] [rom]\n", argv[0]);
+        fprintf(stderr, "Usage: %s [--fullscreen] [--nogl] [rom]\n", argv[0]);
         exit(1);
     }
     
@@ -704,13 +710,15 @@ int main(int argc, char **argv)
         SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN_DESKTOP);
     }
     
-    SDL_GLContext gl_context = SDL_GL_CreateContext(window);
+    gl_context = nogl? NULL : SDL_GL_CreateContext(window);
     
     GLint major = 0, minor = 0;
-    glGetIntegerv(GL_MAJOR_VERSION, &major);
-    glGetIntegerv(GL_MINOR_VERSION, &minor);
+    if (gl_context) {
+        glGetIntegerv(GL_MAJOR_VERSION, &major);
+        glGetIntegerv(GL_MINOR_VERSION, &minor);
+    }
     
-    if (major * 0x100 + minor < 0x302) {
+    if (gl_context && major * 0x100 + minor < 0x302) {
         SDL_GL_DeleteContext(gl_context);
         gl_context = NULL;
     }
diff --git a/SDL/shader.c b/SDL/shader.c
index de2ba564..44de2904 100644
--- a/SDL/shader.c
+++ b/SDL/shader.c
@@ -62,8 +62,11 @@ static GLuint create_program(const char *vsh, const char *fsh)
     return program;
 }
 
+extern bool uses_gl(void);
 bool init_shader_with_name(shader_t *shader, const char *name)
 {
+    if (!uses_gl()) return false;
+    
     GLint major = 0, minor = 0;
     glGetIntegerv(GL_MAJOR_VERSION, &major);
     glGetIntegerv(GL_MINOR_VERSION, &minor);
@@ -187,6 +190,7 @@ void render_bitmap_with_shader(shader_t *shader, void *bitmap, void *previous,
 
 void free_shader(shader_t *shader)
 {
+    if (!uses_gl()) return;
     GLint major = 0, minor = 0;
     glGetIntegerv(GL_MAJOR_VERSION, &major);
     glGetIntegerv(GL_MINOR_VERSION, &minor);