Maintain in-memory copy of the board image

As reading back from the xlib-surface proves incredibly slow (cairo probably
converts the entire image from Xt format to cairo format when we set it
as a source, even though we only want to read a few dozen pixels), we now
keep an exact copy of the board image as a cairo bitmap in memory. This
restores the speed of the animation, but unfortunately leads to awful code.

diff --git a/xboard.c b/xboard.c
index 3041c88..49ab155 100644 (file)
--- a/xboard.c
+++ b/xboard.c
@@ -341,7 +341,7 @@ WindowPlacement wpTags;
 #define SOLID 0
 #define OUTLINE 1
 Boolean cairoAnimate = True;
-static cairo_surface_t *csBoardWindow;
+static cairo_surface_t *csBoardWindow, *csBoardBackup;
 static cairo_surface_t *pngPieceBitmaps[2][(int)BlackPawn];    // scaled pieces as used
 static cairo_surface_t *pngPieceBitmaps2[2][(int)BlackPawn+4]; // scaled pieces in store
 static cairo_surface_t *pngBoardBitmap[2];
@@ -2497,18 +2497,25 @@ do_flash_delay (unsigned long msec)
 }
 
 void
-DrawBorder (int x, int y, int type)
+DoDrawBorder (cairo_surface_t *cs, int x, int y, int type)
 {
     cairo_t *cr;
     DrawSeekOpen();
 
-    cr = cairo_create(csBoardWindow);
+    cr = cairo_create(cs);
     cairo_set_antialias(cr, CAIRO_ANTIALIAS_NONE);
     cairo_rectangle(cr, x, y, squareSize+lineGap, squareSize+lineGap);
     SetPen(cr, lineGap, type == 1 ? appData.highlightSquareColor : appData.premoveHighlightColor, 0);
     cairo_stroke(cr);
 }
 
+void
+DrawBorder (int x, int y, int type)
+{
+  DoDrawBorder(csBoardWindow, x, y, type);
+  DoDrawBorder(csBoardBackup, x, y, type);
+}
+
 static int
 CutOutSquare (int x, int y, int *x0, int *y0, int  kind)
 {
@@ -2563,6 +2570,14 @@ BlankSquare (int x, int y, int color, ChessSquare piece, Drawable dest, int fac)
            cairo_rectangle (cr, x*fac, y*fac, squareSize, squareSize);
            cairo_fill (cr);
            cairo_destroy (cr);
+          if(fac) {
+           cr = cairo_create (csBoardBackup);
+           cairo_set_source_surface (cr, pngBoardBitmap[color], x*fac - x0, y*fac - y0);
+           cairo_set_antialias (cr, CAIRO_ANTIALIAS_NONE);
+           cairo_rectangle (cr, x*fac, y*fac, squareSize, squareSize);
+           cairo_fill (cr);
+           cairo_destroy (cr);
+          }
        } else
        XCopyArea(xDisplay, xpmBoardBitmap[color], dest, wlPieceGC, x0, y0,
                  squareSize, squareSize, x*fac, y*fac);
@@ -2733,6 +2748,10 @@ pngDrawPiece (ChessSquare piece, int square_color, int x, int y, Drawable dest)
     cairo_set_source_surface (cr, pngPieceBitmaps[kind][piece], x, y);
     cairo_paint(cr);
     cairo_destroy (cr);
+    cr = cairo_create (csBoardBackup);
+    cairo_set_source_surface (cr, pngPieceBitmaps[kind][piece], x, y);
+    cairo_paint(cr);
+    cairo_destroy (cr);
 }
 
 typedef void (*DrawFunc)();
@@ -2757,11 +2776,11 @@ ChooseDrawFunc ()
 }
 
 void
-DrawDot (int marker, int x, int y, int r)
+DoDrawDot (int marker, int x, int y, int r, cairo_surface_t *cs)
 {
        cairo_t *cr;
        DrawSeekOpen();
-       cr = cairo_create(csBoardWindow);
+       cr = cairo_create(cs);
        cairo_arc(cr, x+r/2, y+r/2, r/2, 0.0, 2*M_PI);
        if(appData.monoMode) {
            SetPen(cr, 2, marker == 2 ? "#000000" : "#FFFFFF", 0);
@@ -2777,6 +2796,13 @@ DrawDot (int marker, int x, int y, int r)
 }
 
 void
+DrawDot (int marker, int x, int y, int r)
+{
+  DoDrawDot(marker, x, y, r, csBoardWindow);
+  DoDrawDot(marker, x, y, r, csBoardBackup);
+}
+
+void
 DrawOneSquare (int x, int y, ChessSquare piece, int square_color, int marker, char *string, int align)
 {   // basic front-end board-draw function: takes care of everything that can be in square:
     // piece, background, coordinate/count, marker dot
@@ -3007,7 +3033,10 @@ DrawSeekOpen ()
 {
     int boardWidth = lineGap + BOARD_WIDTH * (squareSize + lineGap);
     int boardHeight = lineGap + BOARD_HEIGHT * (squareSize + lineGap);
-    if(!csBoardWindow) csBoardWindow = cairo_xlib_surface_create(xDisplay, xBoardWindow, DefaultVisual(xDisplay, 0), boardWidth, boardHeight);
+    if(!csBoardWindow) {
+       csBoardWindow = cairo_xlib_surface_create(xDisplay, xBoardWindow, DefaultVisual(xDisplay, 0), boardWidth, boardHeight);
+       csBoardBackup = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, boardWidth, boardHeight);
+    }
 }
 
 void
@@ -3016,7 +3045,7 @@ DrawSeekClose ()
 }
 
 void
-DrawGrid()
+DoDrawGrid(cairo_surface_t *cs)
 {
   /* draws a grid starting around Nx, Ny squares starting at x,y */
   int i;
@@ -3024,7 +3053,7 @@ DrawGrid()
 
   DrawSeekOpen();
   /* get a cairo_t */
-  cr = cairo_create (csBoardWindow);
+  cr = cairo_create (cs);
 
   cairo_set_antialias (cr, CAIRO_ANTIALIAS_NONE);
   SetPen(cr, lineGap, "#000000", 0);
@@ -3043,6 +3072,13 @@ DrawGrid()
   return;
 }
 
+void
+DrawGrid()
+{
+  DoDrawGrid(csBoardWindow);
+  DoDrawGrid(csBoardBackup);
+}
+
 /*
  * event handler for redrawing the board
  */
@@ -4039,11 +4075,22 @@ void CopyRectangle (AnimNr anr, int srcBuf, int destBuf,
                 int srcX, int srcY, int width, int height, int destX, int destY)
 {
     if(cairoAnimate) {
-       cairo_t *cr = cairo_create (c_animBufs[anr+destBuf]);
+       cairo_t *cr;// = cairo_create (c_animBufs[anr+destBuf]);
+       cr = cairo_create (c_animBufs[anr+destBuf]);
+       if(c_animBufs[anr+srcBuf] == csBoardWindow)
+       cairo_set_source_surface (cr, csBoardBackup, destX - srcX, destY - srcY);
+       else
+       cairo_set_source_surface (cr, c_animBufs[anr+srcBuf], destX - srcX, destY - srcY);
+       cairo_rectangle (cr, destX, destY, width, height);
+       cairo_fill (cr);
+       cairo_destroy (cr);
+       if(c_animBufs[anr+destBuf] == csBoardWindow) {
+       cr = cairo_create (csBoardBackup); // also draw to backup
        cairo_set_source_surface (cr, c_animBufs[anr+srcBuf], destX - srcX, destY - srcY);
        cairo_rectangle (cr, destX, destY, width, height);
        cairo_fill (cr);
        cairo_destroy (cr);
+       }
     } else
     XCopyArea(xDisplay, animBufs[anr+srcBuf], animBufs[anr+destBuf], animGCs[anr],
                srcX, srcY, width, height, destX, destY);