From 10719139e641edc2b015886b92cf829db80574e5 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Fri, 24 Jul 2009 06:48:35 +0000
Subject: [PATCH] Store dirty rectangles in a structure list. For now there is
 still only one dirty rectangle, but this is the first step to improvement.

---
 caca/caca_internals.h |  10 +++-
 caca/canvas.c         |  12 +++--
 caca/dirty.c          | 122 +++++++++++++++++++++++++++++-------------
 3 files changed, 102 insertions(+), 42 deletions(-)

diff --git a/caca/caca_internals.h b/caca/caca_internals.h
index 5196d6e..267c08f 100644
--- a/caca/caca_internals.h
+++ b/caca/caca_internals.h
@@ -23,6 +23,7 @@ typedef struct caca_figfont caca_figfont_t;
 
 #if !defined(_DOXYGEN_SKIP_ME)
 #   define EVENTBUF_LEN 10
+#   define MAX_DIRTY_COUNT 1
 #endif
 
 struct caca_frame
@@ -60,7 +61,11 @@ struct caca_canvas
 
     /* Dirty rectangles */
     int ndirty;
-    int dirty_xmin, dirty_xmax, dirty_ymin, dirty_ymax;
+    struct
+    {
+        int xmin, xmax, ymin, ymax;
+    }
+    dirty[MAX_DIRTY_COUNT];
 
     /* Shortcut to the active frame information */
     int width, height;
@@ -216,6 +221,9 @@ struct caca_display
     } events;
 };
 
+/* Dirty rectangle functions */
+extern void _caca_clip_dirty_rect_list(caca_canvas_t *);
+
 /* Colour functions */
 extern uint32_t _caca_attr_to_rgb24fg(uint32_t);
 extern uint32_t _caca_attr_to_rgb24bg(uint32_t);
diff --git a/caca/canvas.c b/caca/canvas.c
index 3f070a5..6483bc3 100644
--- a/caca/canvas.c
+++ b/caca/canvas.c
@@ -370,10 +370,17 @@ int caca_resize(caca_canvas_t *cv, int width, int height)
 
     _caca_save_frame_info(cv);
 
+    /* Preload new width and height values into the canvas to optimise
+     * dirty rectangle handling */
     cv->width = width;
     cv->height = height;
     new_size = width * height;
 
+    /* If width or height is smaller (or both), we have the opportunity to
+     * reduce or even remove dirty rectangles */
+    if(width < old_width || height < old_height)
+        _caca_clip_dirty_rect_list(cv);
+
     /* Step 1: if new area is bigger, resize the memory area now. */
     if(new_size > old_size)
     {
@@ -470,9 +477,8 @@ int caca_resize(caca_canvas_t *cv, int width, int height)
         caca_add_dirty_rect(cv, 0, old_height, old_width, height - old_height);
     }
 
-    /* XXX: technically we should not worry about the dirty rectangle in
-     * the bottom-right corner, because we only handle one dirty rectangle,
-     * but in case the API changes later, we make sure this is handled. */
+    /* If both width and height are larger, there is a new dirty rectangle
+     * that needs to be created in the lower right corner. */
     if(width > old_width && height > old_height)
         caca_add_dirty_rect(cv, old_width, old_height,
                             width - old_width, height - old_height);
diff --git a/caca/dirty.c b/caca/dirty.c
index d44ac88..91f7b64 100644
--- a/caca/dirty.c
+++ b/caca/dirty.c
@@ -14,6 +14,14 @@
 
 /*
  *  This file contains the dirty rectangle handling functions.
+ *
+ *
+ *  About dirty rectangles:
+ *
+ *  * Dirty rectangles MUST NOT be larger than the canvas. If the user
+ *  provides a large rectangle through caca_add_dirty_rect(), or if the
+ *  canvas changes size to become smaller, all dirty rectangles MUST
+ *  immediately be clipped to the canvas size.
  */
 
 #include "config.h"
@@ -77,23 +85,12 @@ int caca_get_dirty_rect(caca_canvas_t *cv, int r,
         return -1;
     }
 
-    /* Normalise dirty rectangle so that the values can be directly used. */
-    if(cv->dirty_xmin < 0)
-        cv->dirty_xmin = 0;
-
-    if(cv->dirty_xmax > cv->width - 1)
-        cv->dirty_xmax = cv->width - 1;
+    *x = cv->dirty[r].xmin;
+    *y = cv->dirty[r].ymin;
+    *width = cv->dirty[r].xmax - cv->dirty[r].xmin + 1;
+    *height = cv->dirty[r].ymax - cv->dirty[r].ymin + 1;
 
-    if(cv->dirty_ymin < 0)
-        cv->dirty_ymin = 0;
-
-    if(cv->dirty_ymax > cv->height - 1)
-        cv->dirty_ymax = cv->height - 1;
-
-    *x = cv->dirty_xmin;
-    *y = cv->dirty_ymin;
-    *width = cv->dirty_xmax - cv->dirty_xmin + 1;
-    *height = cv->dirty_ymax - cv->dirty_ymin + 1;
+    debug("dirty #%i: %ix%i at (%i,%i)\n", r, *width, *height, *x, *y);
 
     return 0;
 }
@@ -118,35 +115,49 @@ int caca_get_dirty_rect(caca_canvas_t *cv, int r,
  *  \param height The height of the additional dirty rectangle.
  *  \return 0 in case of success, -1 if an error occurred.
  */
-int caca_add_dirty_rect(caca_canvas_t *cv, int x, int y,
-                             int width, int height)
+int caca_add_dirty_rect(caca_canvas_t *cv, int x, int y, int width, int height)
 {
-    /* Ignore empty and out-of-bounds rectangles */
-    if(width <= 0 || height <= 0 || x + width <= 0 || x >= cv->width
-        || y + height <= 0 || y >= cv->height)
+    debug("new dirty: %ix%i at (%i,%i)\n", width, height, x, y);
+
+    /* Clip arguments to canvas */
+    if(x < 0) { width += x; x = 0; }
+
+    if(x + width > cv->width)
+        width = cv->width - x;
+
+    if(y < 0) { height += y; y = 0; }
+
+    if(y + height > cv->height)
+        height = cv->height - y;
+
+    /* Ignore empty and out-of-canvas rectangles */
+    if(width <= 0 || height <= 0)
     {
         seterrno(EINVAL);
         return -1;
     }
 
-    if(cv->ndirty == 0)
+    /* Add dirty rectangle to list. Current strategy: if there is room
+     * for rectangles, just append it to the list. Otherwise, merge the
+     * new rectangle with the first in the list. */
+    if(cv->ndirty < MAX_DIRTY_COUNT)
     {
-        cv->ndirty = 1;
-        cv->dirty_xmin = x;
-        cv->dirty_xmax = x + width - 1;
-        cv->dirty_ymin = y;
-        cv->dirty_ymax = y + height - 1;
+        cv->dirty[cv->ndirty].xmin = x;
+        cv->dirty[cv->ndirty].xmax = x + width - 1;
+        cv->dirty[cv->ndirty].ymin = y;
+        cv->dirty[cv->ndirty].ymax = y + height - 1;
+        cv->ndirty++;
     }
     else
     {
-        if(x < cv->dirty_xmin)
-            cv->dirty_xmin = x;
-        if(x + width - 1 > cv->dirty_xmax)
-            cv->dirty_xmax = x + width - 1;
-        if(y < cv->dirty_ymin)
-            cv->dirty_ymin = y;
-        if(y + height - 1 > cv->dirty_ymax)
-            cv->dirty_ymax = y + height - 1;
+        if(x < cv->dirty[0].xmin)
+            cv->dirty[0].xmin = x;
+        if(x + width - 1 > cv->dirty[0].xmax)
+            cv->dirty[0].xmax = x + width - 1;
+        if(y < cv->dirty[0].ymin)
+            cv->dirty[0].ymin = y;
+        if(y + height - 1 > cv->dirty[0].ymax)
+            cv->dirty[0].ymax = y + height - 1;
     }
 
     return 0;
@@ -173,9 +184,19 @@ int caca_add_dirty_rect(caca_canvas_t *cv, int x, int y,
 int caca_remove_dirty_rect(caca_canvas_t *cv, int x, int y,
                            int width, int height)
 {
-    /* Ignore empty and out-of-bounds rectangles */
-    if(width <= 0 || height <= 0 || x + width <= 0 || x >= cv->width
-        || y + height <= 0 || y >= cv->height)
+    /* Clip arguments to canvas size */
+    if(x < 0) { width += x; x = 0; }
+
+    if(x + width > cv->width)
+        width = cv->width - x;
+
+    if(y < 0) { height += y; y = 0; }
+
+    if(y + height > cv->height)
+        height = cv->height - y;
+
+    /* Ignore empty and out-of-canvas rectangles */
+    if(width <= 0 || height <= 0)
     {
         seterrno(EINVAL);
         return -1;
@@ -204,3 +225,28 @@ int caca_clear_dirty_rect_list(caca_canvas_t *cv)
     return 0;
 }
 
+/*
+ * XXX: the following functions are local.
+ */
+
+/* Clip all dirty rectangles in case they're larger than the canvas */
+void _caca_clip_dirty_rect_list(caca_canvas_t *cv)
+{
+    int i;
+
+    for(i = 0; i < cv->ndirty; i++)
+    {
+        if(cv->dirty[i].xmin < 0)
+            cv->dirty[i].xmin = 0;
+
+        if(cv->dirty[i].ymin < 0)
+            cv->dirty[i].ymin = 0;
+
+        if(cv->dirty[i].xmax >= cv->width)
+            cv->dirty[i].xmax = cv->width - 1;
+
+        if(cv->dirty[i].ymax >= cv->height)
+            cv->dirty[i].ymax = cv->height - 1;
+    }
+}
+