Merge lp:~widelands-dev/widelands/bug-1536377-fail-gracefully-on-graphics-driver-problems into lp:widelands

[GunChleoc]

Show a basic SDL error message box to the user if the shading language can't be detected or is too old.

Some UI feedback for the user if we can't work with what the graphics driver is giving us.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 4055. State: errored. Details: https://travis-ci.org/widelands/widelands/builds/434035449.
Appveyor build 3851. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_bug_1536377_fail_gracefully_on_graphics_driver_problems-3851.

[Notabilis (notabilis27)]

Diff is looking good. I added a few smaller remarks as comments, though.
Testing by modifying the conditions displayed the message boxes for me.

[GunChleoc (gunchleoc)]

Thanks for the review - comments implemented :)

@bunnybot merge

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 4104. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/439245252.
Appveyor build 3899. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_bug_1536377_fail_gracefully_on_graphics_driver_problems-3899.

=== modified file 'src/graphic/gl/initialize.cc'
--- src/graphic/gl/initialize.cc	2018-09-10 06:11:01 +0000
+++ src/graphic/gl/initialize.cc	2018-10-09 16:40:23 +0000
@@ -20,6 +20,7 @@
 #include "graphic/gl/initialize.h"
 
 #include <csignal>
+#include <cstdlib>
 
 #include <SDL.h>
 
@@ -177,8 +178,30 @@
 	glGetIntegerv(GL_MAX_TEXTURE_SIZE, max_texture_size);
 	log("Graphics: OpenGL: Max texture size: %u\n", *max_texture_size);
 
-	log("Graphics: OpenGL: ShadingLanguage: \"%s\"\n",
-	    reinterpret_cast<const char*>(glGetString(GL_SHADING_LANGUAGE_VERSION)));
+	// TODO(GunChleoc): Localize the on-screen error messages
+	// Exit if we can't detect the shading language version
+	const char* const shading_language_version_string = reinterpret_cast<const char*>(glGetString(GL_SHADING_LANGUAGE_VERSION));
+	if (strcmp(shading_language_version_string, "(null)") == 0) {
+		log("ERROR: Unable to detect the shading language version!\n");
+		SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
+								 "OpenGL Error",
+								 "Widelands won’t work because we were unable to detect the shading language version -- there is an unknown problem with reading the information from the graphics driver.",
+								 NULL);
+		exit(1);
+	}
+
+	log("Graphics: OpenGL: ShadingLanguage: \"%s\"\n", shading_language_version_string);
+
+	// Exit if the shading language version is too old
+	const double shading_language_version = atof(shading_language_version_string);
+	if (shading_language_version < 1.20) {
+		log("ERROR: Shading language version is too old!\n");
+		SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
+								 "OpenGL Error",
+								 "Widelands won’t work because your graphics driver is too old -- version 1.20 or newer is required.",
+								 NULL);
+		exit(1);
+	}
 
 	glDrawBuffer(GL_BACK);