Reverse framebuffer vertical coordinates to start with 0 at top

src/hulk/fb.d

@@ -9,6 +9,8 @@ import hulk.kfont;
 /**
  * Represent a graphical frame buffer.
  *
+ * Coordinate (0,0) is the top-left corner of the framebuffer.
+ *
  * TODO: Handle other pixel formats. Currently only BGRx is supported.
  */
 struct Fb
@@ -80,8 +82,8 @@ struct Fb
     /**
      * Draw a solid rectangle on the framebuffer.
      *
-     * @param x X coordinate of left side of rectangle.
-     * @param y Y coordinate of bottom side of rectangle.
+     * @param x X coordinate of left of rectangle.
+     * @param y Y coordinate of top of rectangle.
      * @param width Width of rectangle.
      * @param height Height of rectangle.
      * @param color Color of rectangle.
@@ -100,7 +102,7 @@ struct Fb
     /**
      * Draw a horizontal line.
      *
-     * @param x X coordinate of left side of line.
+     * @param x X coordinate of left of line.
      * @param y Y coordinate of line.
      * @param width Width of line.
      * @param color Color of line.
@@ -116,7 +118,7 @@ struct Fb
      * Draw a vertical line.
      *
      * @param x X coordinate of line.
-     * @param y Y coordinate of bottom of line.
+     * @param y Y coordinate of top of line.
      * @param height Height of line.
      * @param color Color of line.
      */
@@ -127,7 +129,7 @@ struct Fb
         {
             m_buffer1[buffer_index] = color;
             m_device_buffer[buffer_index] = color;
-            buffer_index -= m_stride;
+            buffer_index += m_stride;
         }
     }
 
@@ -136,8 +138,8 @@ struct Fb
      * The foreground will be white (based on the alpha value), and the
      * background black.
      *
-     * @param x X coordinate of left side of target location.
-     * @param y Y coordinate of bottom side of target location.
+     * @param x X coordinate of left of target location.
+     * @param y Y coordinate of top of target location.
      * @param alpha_bitmap 8-bit alpha-channel bitmap.
      * @param width Bitmap width.
      * @param height Bitmap height.
@@ -145,7 +147,6 @@ struct Fb
     static void blit_alpha_bitmap(size_t x, size_t y, const(ubyte) * alpha_bitmap,
             size_t width, size_t height)
     {
-        y += height - 1u;
         size_t bitmap_index;
         for (size_t iy = 0u; iy < height; iy++)
         {
@@ -158,7 +159,7 @@ struct Fb
                 bitmap_index++;
             }
             memcpy32(&m_device_buffer[row_buffer_index], &m_buffer1[row_buffer_index], width);
-            y--;
+            y++;
         }
     }
 
@@ -167,8 +168,8 @@ struct Fb
      * The foreground will be white (based on the alpha value), and the
      * background black.
      *
-     * @param x X coordinate of left side of target location.
-     * @param y Y coordinate of bottom side of target location.
+     * @param x X coordinate of left of target location.
+     * @param y Y coordinate of top of target location.
      * @param alpha_bitmap 8-bit alpha-channel bitmap.
      * @param width Bitmap width.
      * @param height Bitmap height.
@@ -182,14 +183,14 @@ struct Fb
     /**
      * Copy framebuffer rows up in the framebuffer.
      *
-     * @param y Y coordinate of bottom side of region to copy up.
+     * @param y Y coordinate of top of region to copy up.
      * @param height Height of region to copy up.
      * @param offset Number of rows to copy region up by.
      */
     static void copy_rows_up(size_t y, size_t height, size_t offset)
     {
-        size_t dest_buffer_index = buffer_index(0u, y + height + offset - 1u);
-        size_t src_buffer_index = buffer_index(0u, y + height - 1u);
+        size_t dest_buffer_index = buffer_index(0u, y - offset);
+        size_t src_buffer_index = buffer_index(0u, y);
         memcpy32(&m_buffer1[dest_buffer_index],
                  &m_buffer1[src_buffer_index],
                  (m_stride * height));
@@ -208,6 +209,6 @@ struct Fb
      */
     private static size_t buffer_index(size_t x, size_t y)
     {
-        return (m_height - y - 1u) * m_stride + x;
+        return y * m_stride + x;
     }
 }