From af2178a8da3b0fe33b0a44acb4b89831581b3a30 Mon Sep 17 00:00:00 2001
From: Matthias Goerner <1239022+unhyperbolic@users.noreply.github.com>
Date: Wed, 31 Jan 2024 12:19:25 -0800
Subject: [PATCH] Making SimpleImageShaderWidget use glew so that it works on
 windows.

---
 opengl/CyOpenGL.pyx                          |  7 -------
 opengl/initGlew.pxi                          | 21 ++++++++++----------
 opengl/modern/simple_image_shader_widget.pyx | 11 ++++++++++
 3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/opengl/CyOpenGL.pyx b/opengl/CyOpenGL.pyx
index c453642c..5386ecb1 100644
--- a/opengl/CyOpenGL.pyx
+++ b/opengl/CyOpenGL.pyx
@@ -108,13 +108,6 @@ class RawOpenGLWidget(Tk_.Widget, Tk_.Misc):
         # initialize
         self.make_current()
 
-        # If we are using GLEW, call glewInit.
-        # This will set all gl function pointers.
-        cdef GLenum err
-        err = callGlewInitIfNecessary()
-        if err != 0:
-            raise Exception("Failed to initialize GLEW: %d" % err)
-
         # Check that GLEW set all function pointers that we are calling
         # below.
         cdef char * missing_gl_function
diff --git a/opengl/initGlew.pxi b/opengl/initGlew.pxi
index 64768fad..bdc79363 100644
--- a/opengl/initGlew.pxi
+++ b/opengl/initGlew.pxi
@@ -5,23 +5,17 @@
 
 cdef extern from *:
     """
-    int callGlewInitIfNecessary()
-    {
-
-    #ifdef USE_GLEW
-        return glewInit();
-    #else
-        return 0;
-    #endif
-
-    }
-
     #define CHECK_GLEW_FOR_FUNCTION(name) if (!name) { return #name; }
 
     /* Check that GLEW set the gl function pointers */
     char * checkGlewForLegacyOpenGL()
     {
     #ifdef USE_GLEW
+        GLenum err = glewInit();
+        if (err != 0) {
+            return "glewInit failed";
+        }
+
         CHECK_GLEW_FOR_FUNCTION(glMatrixMode);
         CHECK_GLEW_FOR_FUNCTION(glLoadIdentity);
         CHECK_GLEW_FOR_FUNCTION(glOrtho);
@@ -82,6 +76,11 @@ cdef extern from *:
     char * checkGlewForModernOpenGL()
     {
     #ifdef USE_GLEW
+        GLenum err = glewInit();
+        if (err != 0) {
+            return "glewInit failed";
+        }
+
         CHECK_GLEW_FOR_FUNCTION(glCreateShader);
         CHECK_GLEW_FOR_FUNCTION(glAttachShader);
         CHECK_GLEW_FOR_FUNCTION(glShaderSource);
diff --git a/opengl/modern/simple_image_shader_widget.pyx b/opengl/modern/simple_image_shader_widget.pyx
index 79d25bd1..5e7ac23d 100644
--- a/opengl/modern/simple_image_shader_widget.pyx
+++ b/opengl/modern/simple_image_shader_widget.pyx
@@ -56,6 +56,17 @@ class SimpleImageShaderWidget(GLCanvas):
         self.textures = []
         self.report_time_callback = None
 
+        self.make_current()
+
+        cdef char * missing_gl_function
+        missing_gl_function = checkGlewForModernOpenGL()
+        if missing_gl_function:
+            raise Exception(
+                ("Missing gl function: %s. Your graphics card probably does "
+                 "not support the required OpenGL version (3.2 or later). Your "
+                 "OpenGL version is %s.") % (missing_gl_function,
+                                             get_gl_string('GL_VERSION')))
+
     def set_textures(self, texture_files):
         self.make_current()