Reverse framebuffer vertical coordinates to start with 0 at top

src/hulk/console.d

@@ -6,6 +6,11 @@ module hulk.console;
 import hulk.fb;
 import hulk.kfont;
 
+/**
+ * Represent the HULK console.
+ *
+ * Coordinate (0,0) is the top-left console position.
+ */
 struct Console
 {
     /** Console width in text columns. */
@@ -64,7 +69,7 @@ struct Console
         if (m_y == m_height)
         {
             m_y--;
-            Fb.copy_rows_up(fb_y(m_height - 1u),
+            Fb.copy_rows_up(fb_y(1u),
                     (m_height - 1u) * Kfont.line_height,
                     Kfont.line_height);
             Fb.rect(0u, fb_y(m_height - 1u), fb_x(m_width), Kfont.line_height, 0u);
@@ -81,7 +86,7 @@ struct Console
     private static void render_char(size_t x, size_t y, char ch)
     {
         const(CharInfo) * ci = &Kfont.chars[ch];
-        Fb.blit_alpha_bitmap(fb_x(x) + ci.left, fb_y(y) + Kfont.baseline_offset + ci.top - ci.height, ci.bitmap, ci.width, ci.height);
+        Fb.blit_alpha_bitmap(fb_x(x) + ci.left, fb_y(y) + Kfont.line_height - Kfont.baseline_offset - ci.top, ci.bitmap, ci.width, ci.height);
     }
 
     /**
@@ -97,6 +102,6 @@ struct Console
      */
     private static size_t fb_y(size_t y)
     {
-        return Fb.height - ((y + 1u) * Kfont.line_height);
+        return y * Kfont.line_height;
     }
 }

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 x X coordinate of left of rectangle.
-     * @param y Y coordinate of bottom side 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 x X coordinate of left of target location.
-     * @param y Y coordinate of bottom side 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 x X coordinate of left of target location.
-     * @param y Y coordinate of bottom side 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 dest_buffer_index = buffer_index(0u, y - offset);
-        size_t src_buffer_index = buffer_index(0u, y + height - 1u);
+        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;
     }
 }