From 17edc0a9d68982c07b3f537333c59da2271f76a7 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Tue, 13 Oct 2015 21:38:24 -0400
Subject: [PATCH] redraw on a timer; rotate quad

---
 app.cc | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/app.cc b/app.cc
index 6a180ea..26bec2d 100644
--- a/app.cc
+++ b/app.cc
@@ -67,7 +67,6 @@ bool init(void)
         glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (void *)(3 * sizeof(GLfloat)));
         glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (void *)(6 * sizeof(GLfloat)));
 
-        modelview = glm::translate(glm::mat4(1.0), glm::vec3(0, 0, -2));
         projection = glm::perspective(60.0f, (float)WIDTH / (float)HEIGHT, 0.1f, 1000.0f);
 
         for (int i = 0; i < 16; i++)
@@ -106,12 +105,13 @@ bool init(void)
     return true;
 }
 
-void display(SDL_Window * window)
+static void draw_cube()
 {
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+    glm::mat4 modelview_backup = modelview;
 
     program->use();
     cube_array->bind();
+
     glUniform4f(uniforms.ambient, 1.0, 1.0, 1.0, 1.0);
     glUniform4f(uniforms.specular, 1.0, 1.0, 1.0, 1.0);
     glUniform1f(uniforms.shininess, 150.0);
@@ -119,13 +119,30 @@ void display(SDL_Window * window)
     glUniformMatrix4fv(uniforms.modelview, 1, GL_FALSE, &modelview[0][0]);
     glUniformMatrix4fv(uniforms.projection, 1, GL_FALSE, &projection[0][0]);
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
+}
+
+void display(SDL_Window * window)
+{
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+    modelview = glm::translate(glm::mat4(1.0), glm::vec3(0, 0, -2));
+    modelview = glm::rotate(modelview, (float)(SDL_GetTicks() / 1000.0), glm::vec3(0, 1, 0));
+
+    draw_cube();
 
     SDL_GL_SwapWindow(window);
 }
 
+static SDL_Event UpdateEvent;
+
+static Uint32 UpdateCallback(Uint32 interval, void * param)
+{
+    SDL_PushEvent(&UpdateEvent);
+    return interval;
+}
+
 int main(int argc, char *argv[])
 {
-    if (SDL_Init(SDL_INIT_VIDEO))
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER))
     {
         printf("Failed to initialize SDL!\n");
         return 1;
@@ -164,6 +181,9 @@ int main(int argc, char *argv[])
         return 2;
     }
 
+    UpdateEvent.type = SDL_USEREVENT;
+    UpdateEvent.user.code = 0;
+    SDL_AddTimer(25, UpdateCallback, NULL);
     display(window);
     SDL_Event event;
     while (SDL_WaitEvent(&event))
@@ -177,5 +197,9 @@ int main(int argc, char *argv[])
             if (event.key.keysym.sym == SDLK_RETURN)
                 display(window);
         }
+        else if (event.type == SDL_USEREVENT)
+        {
+            display(window);
+        }
     }
 }