Restore default caps in GLFW/SDL demos #105

All modifed state changed by the demo rendering functions is now set
to default values after being called. I tried to save and restore all
relavent state but for some reason function glBlendEquationSeperate
is not defined for me. So I decided to make it as easy as possible
for me and just set everything to default. This means you have to
either save and restore or reset your own OpenGL state after calling
`nk_xxx_render`. I know it is not perfect but I have no better
solution at this point in time.

demo/glfw/main.c

@@ -128,6 +128,10 @@ int main(void)
         glViewport(0, 0, width, height);
         glClear(GL_COLOR_BUFFER_BIT);
         glClearColor(bg[0], bg[1], bg[2], bg[3]);
+        /* IMPORTANT: `nk_sdl_render` modifies some global OpenGL state
+         * with blending, scissor, face culling and depth test and defaults everything
+         * back into a default state. Make sure to either save and restore or
+         * reset your own state after drawing rendering the UI. */
         nk_glfw3_render(NK_ANTI_ALIASING_ON, MAX_VERTEX_BUFFER, MAX_ELEMENT_BUFFER);
         glfwSwapBuffers(win);}
     }

demo/glfw/nuklear_glfw.c

@@ -153,8 +153,6 @@ nk_glfw3_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element
 {
     struct nk_glfw_device *dev = &glfw.ogl;
     int width, height;
-    GLint last_prog, last_tex;
-    GLint last_ebo, last_vbo, last_vao;
     GLfloat ortho[4][4] = {
         {2.0f, 0.0f, 0.0f, 0.0f},
         {0.0f,-2.0f, 0.0f, 0.0f},
@@ -165,13 +163,6 @@ nk_glfw3_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element
     ortho[0][0] /= (GLfloat)width;
     ortho[1][1] /= (GLfloat)height;
 
-    /* save previous opengl state */
-    glGetIntegerv(GL_CURRENT_PROGRAM, &last_prog);
-    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_tex);
-    glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_vao);
-    glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_ebo);
-    glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vbo);
-
     /* setup global state */
     glEnable(GL_BLEND);
     glBlendEquation(GL_FUNC_ADD);
@@ -236,12 +227,12 @@ nk_glfw3_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element
         nk_clear(&glfw.ctx);
     }
 
-    /* restore old state */
-    glUseProgram((GLuint)last_prog);
-    glBindTexture(GL_TEXTURE_2D, (GLuint)last_tex);
-    glBindBuffer(GL_ARRAY_BUFFER, (GLuint)last_vbo);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, (GLuint)last_ebo);
-    glBindVertexArray((GLuint)last_vao);
+    /* default OpenGL state */
+    glUseProgram(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+    glDisable(GL_BLEND);
     glDisable(GL_SCISSOR_TEST);
 }
 

demo/sdl/main.c

@@ -132,6 +132,10 @@ main(int argc, char* argv[])
         glViewport(0, 0, win_width, win_height);
         glClear(GL_COLOR_BUFFER_BIT);
         glClearColor(bg[0], bg[1], bg[2], bg[3]);
+        /* IMPORTANT: `nk_sdl_render` modifies some global OpenGL state
+         * with blending, scissor, face culling and depth test and defaults everything
+         * back into a default state. Make sure to either save and restore or
+         * reset your own state after drawing rendering the UI. */
         nk_sdl_render(NK_ANTI_ALIASING_ON, MAX_VERTEX_MEMORY, MAX_ELEMENT_MEMORY);
         SDL_GL_SwapWindow(win);}
     }

demo/sdl/nuklear_sdl.c

@@ -145,10 +145,9 @@ nk_sdl_device_destroy(void)
 NK_API void
 nk_sdl_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element_buffer)
 {
+
     struct nk_sdl_device *dev = &sdl.ogl;
     int width, height;
-    GLint last_prog, last_tex;
-    GLint last_ebo, last_vbo, last_vao;
     GLfloat ortho[4][4] = {
         {2.0f, 0.0f, 0.0f, 0.0f},
         {0.0f,-2.0f, 0.0f, 0.0f},
@@ -159,13 +158,6 @@ nk_sdl_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element_b
     ortho[0][0] /= (GLfloat)width;
     ortho[1][1] /= (GLfloat)height;
 
-    /* save previous opengl state */
-    glGetIntegerv(GL_CURRENT_PROGRAM, &last_prog);
-    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_tex);
-    glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_vao);
-    glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_ebo);
-    glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vbo);
-
     /* setup global state */
     glEnable(GL_BLEND);
     glBlendEquation(GL_FUNC_ADD);
@@ -230,12 +222,11 @@ nk_sdl_render(enum nk_anti_aliasing AA, int max_vertex_buffer, int max_element_b
         nk_clear(&sdl.ctx);
     }
 
-    /* restore old state */
-    glUseProgram((GLuint)last_prog);
-    glBindTexture(GL_TEXTURE_2D, (GLuint)last_tex);
-    glBindBuffer(GL_ARRAY_BUFFER, (GLuint)last_vbo);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, (GLuint)last_ebo);
-    glBindVertexArray((GLuint)last_vao);
+    glUseProgram(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+    glDisable(GL_BLEND);
     glDisable(GL_SCISSOR_TEST);
 }