Major refactoring, got working with color changes

blit_xcb.c

@@ -1,5 +1,3 @@
-#include <GL/gl.h>
-#include <GL/glx.h>
 #include <X11/Xlib-xcb.h> /* for XGetXCBConnection, link with libX11-xcb */
 #include <X11/Xlib.h>
 #include <assert.h>
@@ -8,14 +6,18 @@
 #include <time.h>
 #include <unistd.h>
 #include <xcb/xcb.h>
-#include <xcb/xcb.h>
+
+typedef struct {
+  unsigned short r;
+  unsigned short g;
+  unsigned short b;
+} color_t;
 
 xcb_alloc_color_reply_t*
-getColor(xcb_connection_t*,
+getColorFromCmap(xcb_connection_t*,
-         xcb_colormap_t,
+                 xcb_colormap_t,
-         unsigned short,
+                 color_t);
-         unsigned short,
+
-         unsigned short);
 
 /* Macro definition to parse X server events
  * The ~0x80 is needed to get the lower 7 bits
@@ -33,7 +35,6 @@ getColor(xcb_connection_t*,
  * Figure out what resources need to be free'd and figure out a strategy for allocating things better
  * Figure out a better way of managing the event loop than nanosleep? (clock_nanosleep maybe)
  * Figure out which events we need to actually be handling
- * Figure out how to resize dynamically (See handmade hero videos for tips)
  * Figure out good strategy for only copying changed pixels to window
  * Figure out what allocations can fail and what to do if they fail
  */
@@ -111,20 +112,18 @@ allocateColorMap(xcb_connection_t *display,
 }
 
 xcb_alloc_color_reply_t*
-getColor(xcb_connection_t *display,
+getColorFromCmap(xcb_connection_t *display,
-         xcb_colormap_t colormap,
+                 xcb_colormap_t colormap,
-         unsigned short red,
+                 color_t color) {
-         unsigned short green,
+  /* Allocate a color in the color map */
-         unsigned short blue) {
-  /* Return a new xcb color structure */
   /* Initialize it with RGB */
 
   xcb_alloc_color_reply_t *reply = xcb_alloc_color_reply(display,
                                                          xcb_alloc_color(display,
                                                                          colormap,
-                                                                         red,
+                                                                         color.r,
-                                                                         green,
+                                                                         color.g,
-                                                                         blue),
+                                                                         color.b),
                                                          NULL);
 
   /* TODO, make sure colors get free'd after they're used?
@@ -149,19 +148,15 @@ static xcb_gcontext_t
 getGC(xcb_connection_t *display,
       xcb_screen_t *screen,
       xcb_colormap_t colormap,
-      unsigned short r,
+      color_t color) {
-      unsigned short g,
-      unsigned short b) {
 
   xcb_drawable_t window = screen->root;
 
   xcb_gcontext_t foreground = xcb_generate_id(display);
 
-  xcb_alloc_color_reply_t *xcolor = getColor(display,
+  xcb_alloc_color_reply_t *xcolor = getColorFromCmap(display,
-                                             colormap,
+                                                     colormap,
-                                             r,
+                                                     color);
-                                             g,
-                                             b);
 
   uint32_t mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
   uint32_t values[2] = {xcolor->pixel, 0};
@@ -175,35 +170,36 @@ getGC(xcb_connection_t *display,
   return foreground;
 }
 
-static xcb_pixmap_t
+static xcb_void_cookie_t
-allocatePixmap(xcb_connection_t *display,
+updateGCColor(xcb_connection_t *display,
-               xcb_screen_t *screen,
+              xcb_gcontext_t gc,
-               xcb_window_t window,
+              xcb_colormap_t colormap,
-               uint32_t width,
+              color_t color) {
-               uint32_t height) {
+  /* https://www.x.org/releases/X11R7.6/doc/libxcb/tutorial/index.html#changegc */
-  xcb_pixmap_t pixmapId = xcb_generate_id(display);
-
-  xcb_create_pixmap(display,
-                    screen->root_depth,
-                    pixmapId,
-                    window,
-                    width,
-                    height);
 
-  return pixmapId;
+  xcb_alloc_color_reply_t *xcolor = getColorFromCmap(display,
+                                                     colormap,
+                                                     color);
+
+  uint32_t mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
+  uint32_t values[2] = {xcolor->pixel, 0};
+
+  return xcb_change_gc(display,
+                       gc,
+                       mask,
+                       values);
 }
 
 xcb_point_t*
 genPoints(uint16_t width,
           uint16_t height) {
+  /* Fills the entire screen with pixels */
   xcb_point_t *points = malloc( sizeof(xcb_point_t) * height * width);
 
   xcb_point_t point;
 
   int i = 0;
 
-  printf("width = %d, height = %d\n", width, height);
-
   for (uint16_t x = 0; x < width; x++) {
     for(uint16_t y = 0; y < height; y++) {
       point.x = x;
@@ -218,17 +214,101 @@ genPoints(uint16_t width,
   return points;
 }
 
+void
+displayBuffer(xcb_pixmap_t pixmap_buffer,
+              xcb_connection_t *display,
+              xcb_window_t window,
+              xcb_gcontext_t gc,
+              xcb_expose_event_t *event) {
+  /* Note that x = 0, y = 0, is the top left of the screen */
+  xcb_copy_area(display,
+                pixmap_buffer,
+                window,
+                gc,
+                0, /* top left x coord */
+                0, /* top left y coord */
+                event->x, /* top left x coord of dest*/
+                event->y, /* top left y coord of dest*/
+                event->width, /* pixel width of source */
+                event->height /* pixel height of source */
+                );
+
+  xcb_flush(display);
+}
+
+void
+writePixmap(xcb_pixmap_t pixmap_buffer,
+            color_t color,
+            xcb_colormap_t colormap,
+            xcb_point_t *points,
+            xcb_gcontext_t gc,
+            xcb_connection_t *display,
+            xcb_window_t window,
+            xcb_expose_event_t *event) {
+
+  printf("Drawing pixmap\nr = %u, g = %u, b = %u\n", color.r, color.g, color.b);
+  updateGCColor(display,
+                gc,
+                colormap,
+                color);
+
+  xcb_poly_point(display,
+                 XCB_COORD_MODE_ORIGIN, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */
+                 pixmap_buffer,
+                 gc,
+                 event->width*event->height,
+                 points);
+
+  displayBuffer(pixmap_buffer,
+                display,
+                window,
+                gc,
+                event);
+
+}
+
+xcb_pixmap_t
+getPixmap(xcb_connection_t *display,
+          xcb_screen_t *screen,
+          xcb_window_t window,
+          uint16_t window_width,
+          uint16_t window_height) {
+    /* Allocate a pixmap we will be blitting to the window */
+    xcb_pixmap_t pixmapId = xcb_generate_id(display);
+
+    xcb_create_pixmap(display,
+                      screen->root_depth,
+                      pixmapId,
+                      window,
+                      window_width,
+                      window_height);
+
+    return pixmapId;
+}
+
+static color_t
+color(unsigned short r,
+      unsigned short g,
+      unsigned short b) {
+  /* Initialize an RGB color struct */
+  color_t color;
+  color.r = r;
+  color.g = g;
+  color.b = b;
+  return color;
+}
+
 int
 main(void) {
-  uint16_t window_width = 500;
-  uint16_t window_height = 500;
-
   /* Open up the display */
   xcb_connection_t *display = getDisplay();
 
   /* Get a handle to the screen */
   xcb_screen_t *screen = getScreen(display);
 
+  uint16_t window_height = screen->height_in_pixels;
+  uint16_t window_width = screen->width_in_pixels;
+
   /* Create a window */
   xcb_window_t window = getWindow(display,
                                   screen,
@@ -248,15 +328,25 @@ main(void) {
   struct timespec req = genSleep(0, 20000000);
   struct timespec rem = genSleep(0, 0);
 
+  color_t draw_color = color(0, 0, 0);
+
   xcb_generic_event_t *event;
   xcb_expose_event_t *expose;
 
   xcb_gcontext_t gc = getGC(display,
                             screen,
                             colormap,
-                            0,
+                            draw_color);
-                            0xffff,
+
-                            0);
+  /* The pixmap that acts as our backbuffer */
+  xcb_pixmap_t pixmap_buffer = getPixmap(display,
+                                         screen,
+                                         window,
+                                         window_width,
+                                         window_height);
+
+  int was_exposed = 0;
+
   while (1) {
     event = xcb_poll_for_event(display);
 
@@ -267,59 +357,24 @@ main(void) {
 
         case XCB_EXPOSE: {
           expose = (xcb_expose_event_t *)event;
+          window_width = expose->width;
+          window_height = expose->height;
           printf("Window %u exposed. Region to be redrawn at location (%u,%u), with dimension (%u,%u)\n",
                  expose->window, expose->x,
                  expose->y,
                  expose->width,
                  expose->height);
 
-          window_width = expose->width;
-          window_height = expose->height;
-
-          /*
-           * One important note should be made:
-           * it is possible to create pixmaps with different depths on the same screen.
-           * When we perform copy operations (a pixmap onto a window, etc),
-           * we should make sure that both source and target have the same depth.
-           * If they have a different depth, the operation will fail.
-           * The exception to this is if we copy a specific bit plane of the source pixmap using xcb_copy_plane().
-           * In such an event, we can copy a specific plane to the target window
-           * (in actuality, setting a specific bit in the color of each pixel copied).
-           * This can be used to generate strange graphic effects in a window, but that is beyond the scope of this tutorial.
-           */
-
-
-          /* Allocate a pixmap we will be blitting to the window */
-          xcb_pixmap_t pixmap = allocatePixmap(display,
-                                               screen,
-                                               window,
-                                               window_width,
-                                               window_height);
-
           xcb_point_t *points = genPoints(window_width, window_height);
-
+          writePixmap(pixmap_buffer,
-          xcb_poly_point (display,               /* The connection to the X server */
+                      draw_color,
-                          XCB_COORD_MODE_ORIGIN, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */
+                      colormap,
-                          pixmap,        /* The drawable on which we want to draw the point(s) */
+                      points,
-                          gc,              /* The Graphic Context we use to draw the point(s) */
+                      gc,
-                          window_width*window_height,      /* The number of points */
+                      display,
-                          points);         /* An array of points */
+                      window,
-
+                      expose);
-          xcb_copy_area(display,
+          was_exposed = 1;
-                        pixmap,
-                        window,
-                        gc,
-                        0, /* top left x coord */
-                        0, /* top left y coord */
-                        0, /* top left x coord of dest*/
-                        0, /* top left y coord of dest*/
-                        window_width, /* pixel width of source */
-                        window_height /* pixel height of source */
-                        );
-
-          xcb_flush(display);
-          free(points);
-          xcb_free_pixmap(display, pixmap);
           break;
         }
 
@@ -331,10 +386,29 @@ main(void) {
         free(event);
       }
     }
+    if (was_exposed) {
+      xcb_point_t *points = genPoints(window_width, window_height);
+
+      writePixmap(pixmap_buffer,
+                  draw_color,
+                  colormap,
+                  points,
+                  gc,
+                  display,
+                  window,
+                  expose);
+    }
+
+    draw_color.r += 100;
+
+    /* General strategy for writing to buffer
+     * Function should take point(s), color, and write it
+     */
 
     nanosleep(&req, &rem);
   }
 
+  xcb_free_pixmap(display, pixmap_buffer);
   xcb_disconnect(display);
   return 0;