Extend full-board textures by periodic tiling (XB)

Texture images with an -NxM suffix to their name are scaled to match
that number of squares before cutting squares out of them. But if the
actual board was larger than NxM the remaining squares fell outside the
image and remained white. Now the cutting area is mapped back into
the image, effectively behaving as if it is periodically tiling the
entire plane.

diff --git a/draw.c b/draw.c
index 6df1a13..4ad6887 100644 (file)
--- a/draw.c
+++ b/draw.c
@@ -269,6 +269,8 @@ ExposeRedraw (Option *graph, int x, int y, int w, int h)
     cairo_destroy(cr);
 }
 
+static int modV[2], modH[2];
+
 static void
 CreatePNGBoard (char *s, int kind)
 {
@@ -286,13 +288,14 @@ CreatePNGBoard (char *s, int kind)
            useTexture |= kind + 1; pngOriginalBoardBitmap[kind] = img;
            w = textureW[kind] = cairo_image_surface_get_width (img);
            h = textureH[kind] = cairo_image_surface_get_height (img);
-           n[kind] = 1.;
+           n[kind] = 1.; modV[kind] = modH[kind] = -1;
            while((q = strchr(p+1, '-'))) p = q; // find last '-'
            if(strlen(p) < 11 && sscanf(p, "-%dx%d.pn%c", &f, &r, &c) == 3 && c == 'g') {
                if(f == 0 || r == 0) f = BOARD_WIDTH, r = BOARD_HEIGHT; // 0x0 means 'fits any', so make it fit
                textureW[kind] = (w*BOARD_WIDTH)/f; // sync cutting locations with square pattern
                textureH[kind] = (h*BOARD_HEIGHT)/r;
                n[kind] = r*squareSize/h; // scale to make it fit exactly vertically
+               modV[kind] = r; modH[kind] = f;
            } else
            if((p = strstr(s, "xq")) && (p == s || p[-1] == '/')) { // assume full-board image for Xiangqi
                while(0.8*squareSize*BOARD_WIDTH > n[kind]*w || 0.8*squareSize*BOARD_HEIGHT > n[kind]*h) n[kind]++;
@@ -672,6 +675,7 @@ CutOutSquare (int x, int y, int *x0, int *y0, int  kind)
     int nx = x/(squareSize + lineGap), ny = y/(squareSize + lineGap);
     *x0 = 0; *y0 = 0;
     if(textureW[kind] < squareSize || textureH[kind] < squareSize) return 0;
+    if(modV[kind] > 0) nx %= modH[kind], ny %= modV[kind]; // tile fixed-format board periodically to extend it
     if(textureW[kind] < W*squareSize)
        *x0 = (textureW[kind] - squareSize) * nx/(W-1);
     else