Improve basic programs page with better code

It did not make sense for me that the SDL2 and shape example looks
slightly different. While changing this I also found some bugs in some
of the examples and make the text look a little bit better. Hope this
isn't too much for one PR.

_includes/samples/sdl2/main.c

@@ -20,17 +20,22 @@ int main(int argc, char *argv[])
     int running = 1;
     SDL_Event event;
     while (running) { 
+        // Process input
         if (SDL_PollEvent(&event)) {
             switch (event.type) {
                 case SDL_QUIT:
+                    // If the close button is pressed on pc, close the program
                     running = 0;
                     break;
                 case SDL_CONTROLLERDEVICEADDED:
+                    // Connect a controller when it is connected
                     SDL_GameControllerOpen(event.cdevice.which);
                     break;
                 case SDL_CONTROLLERBUTTONDOWN:
-                    if(event.cbutton.button == SDL_CONTROLLER_BUTTON_START)
+                    if(event.cbutton.button == SDL_CONTROLLER_BUTTON_START) {
+                        // Close the program if start is pressed
                         running = 0;
+                    }
                     break;
             }
         }

_includes/samples/shape/main.c

@@ -12,6 +12,25 @@ PSP_MAIN_THREAD_ATTR(THREAD_ATTR_VFPU | THREAD_ATTR_USER);
 
 char list[0x20000] __attribute__((aligned(64)));
 
+int exit_callback(int arg1, int arg2, void *common) {
+    sceKernelExitGame();
+    return 0;
+}
+
+int callback_thread(SceSize args, void *argp) {
+    int cbid = sceKernelCreateCallback("Exit Callback", exit_callback, NULL);
+    sceKernelRegisterExitCallback(cbid);
+    sceKernelSleepThreadCB();
+    return 0;
+}
+
+int setup_callbacks(void) {
+    int thid = sceKernelCreateThread("update_thread", callback_thread, 0x11, 0xFA0, 0, 0);
+    if(thid >= 0)
+        sceKernelStartThread(thid, 0, 0);
+    return thid;
+}
+
 void initGu(){
     sceGuInit();
 
@@ -67,21 +86,26 @@ void drawRect(float x, float y, float w, float h) {
     vertices[0].x = x;
     vertices[0].y = y;
 
-    vertices[1].x = y + w;
-    vertices[1].y = x + h;
+    vertices[1].x = x + w;
+    vertices[1].y = y + h;
 
     sceGuColor(0xFF0000FF); // Red, colors are ABGR
     sceGuDrawArray(GU_SPRITES, GU_TEXTURE_16BIT | GU_VERTEX_16BIT | GU_TRANSFORM_2D, 2, 0, vertices);
 }
 
 
 int main() {
+    // Make exiting with the home button possible
+    setup_callbacks();
+
+    // Setup the library used for rendering
     initGu();
+
     int running = 1;
     while(running){
         startFrame();
 
-        drawRect(32, 32, 64, 64);
+        drawRect(216, 96, 34, 64);
 
         endFrame();
     }

basic_programs.md

@@ -12,7 +12,7 @@ nav_order: 3
 
 ![](images/hello.png)
 
-> This is a simple Hello World program for the PSP.
+This is a simple Hello World program for the PSP.
 
 Click on view source below to see the code and how to build it.
 
@@ -50,7 +50,7 @@ This will result in an EBOOT.PBP file in the build directory. Put it in a direct
 
 ![](images/shape.png)
 
-> This is a simple square drawn on the PSP. It uses the native libgu library. 
+This is a simple square drawn on the PSP. It uses the native libgu library. 
 
 Click on view source below to see the code and how to build it.
 
@@ -89,7 +89,7 @@ More libgu examples can be found <a href="https://github.com/pspdev/pspsdk/tree/
 
 ![](images/controls.png)
 
-> This is a simple program to use the PSP's input functions.
+This is a simple program to use the PSP's input functions.
 
 Click on view source below to see the code and how to build it.
 
@@ -126,7 +126,7 @@ make
 
 ![](images/audio.png)
 
-> This is a simple program to use the audio of the PSP with minimal effort. It uses native audio library. 
+This is a simple program to use the audio of the PSP with minimal effort. It uses native audio library. 
 
 Click on view source below to see the code and how to build it.
 
@@ -163,9 +163,11 @@ More audiolib examples can be found <a href="https://github.com/pspdev/pspsdk/tr
 ## Using SDL2
 {: .fs-6 .fw-700 }
 
-![](images/sdl2.png)
+![](images/shape.png)
+
+SDL2 is a library which handles system specific things like input, audio and window management for you. It can also be used to render shapes and images, just like the native libgu. This can be slower, but will result in code that is easier to read and can run on multiple platforms.
 
-> SDL2 is a library which handles system specific things like input, audio and window management for you. It can also be used to render shapes and images, just like the native libgu. This will be slower, but will result in code that can be run more easily on multiple platforms. 
+Despite this example adding an option to close by pressing the start button, the code is much shorter. It can even be build for Linux without any further modifications.
 
 Click on view source below for the to see the code and how to build it.
 
@@ -212,7 +214,7 @@ More documentation on SDL can be found <a href="http://wiki.libsdl.org/FrontPage
 
 ![](images/sdl2_mixer.png)
 
-> This is a simple program to use the SDL2_mixer library. It handle audio playback in multimedia applications and games. It supports various audio formats(MP3/OGG).
+This is a simple program to use the SDL2_mixer library. It handle audio playback in multimedia applications and games. It supports various audio formats(MP3/OGG).
 
 Click on view source below to see the code and how to build it.
 
@@ -249,7 +251,7 @@ This will result in an EBOOT.PBP file in the build directory. Put it in a direct
 
 ![](images/sdl2_ttf.jpg)
 
-> This is a simple program to use the SDL2_ttf library. It provides functionality for rendering TrueType fonts for your PSP.
+This is a simple program to use the SDL2_ttf library. It provides functionality for rendering TrueType fonts for your PSP.
 
 Click on view source below to see the code and how to build it.