Fix 998529, mono (invert) cursors not visible on a black background, by doing
simple edge detection on the cursor (this is done once when the cursor
is changed and then cached, cursors are 32x32 generally) and thus having
a cursor with contrast on both dark and light backgrounds.
When (if) GDK gets invert cursor support (wayland?) then we can just use
the cursor as is. Until then X doesn't provide any way I see of solving
this otherwise. The end result was tested with the I beam cursor that
the original bug was referring to (run putty on a windows 7 vm) and
looks ok to me.
---
gtk/channel-cursor.c | 86 ++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 66 insertions(+), 20 deletions(-)
diff --git a/gtk/channel-cursor.c b/gtk/channel-cursor.c
index 66e91df..2c48d37 100644
--- a/gtk/channel-cursor.c
+++ b/gtk/channel-cursor.c
@@ -275,15 +275,67 @@ static void print_cursor(display_cursor *cursor, const guint8 *data)
}
#endif
+static bool cursor_xor_pixel(const guint8 *xor, int bpl, int x, int y)
+{
+ return (xor[bpl * y + (x / 8)] & (0x80 >> (x % 8))) > 0;
+}
+
+static guint8 cursor_is_xor_edge(display_cursor *cursor, const guint8 *xor, int bpl, int x, int y)
+{
+ if (x == 0 || x == cursor->hdr.width -1 || y == 0 || y == cursor->hdr.height - 1) {
+ return 0;
+ }
+#define P(x, y) cursor_xor_pixel(xor, bpl, x, y)
+ return !P(x, y) && (P(x - 1, y + 1) || P(x, y + 1) || P(x + 1, y + 1) ||
+ P(x - 1, y) || P(x + 1, y) ||
+ P(x - 1, y - 1) || P(x, y - 1) || P(x + 1, y - 1));
+#undef P
+}
+
+static bool cursor_is_and_ones(display_cursor *cursor, const guint8 *data)
+{
+ int x, y, bpl;
+
+ bpl = (cursor->hdr.width + 7) / 8;
+ for (y = 0 ; y < cursor->hdr.height; ++y) {
+ for (x = 0 ; x < cursor->hdr.width / 8; ++x) {
+ if (data[x] != 0xff) {
+ return false;
+ }
+ }
+ data += bpl;
+ }
+ return true;
+}
+
+/* Mono cursors have two places, "and" and "xor". If a bit is 1 in both, it
+ * means invertion of the corresponding pixel in the display. Since X11 (and
+ * gdk) doesn't do invertion, instead we do edge detection and turn the
+ * sorrounding edge pixels black, and the invert-me pixels white. To
+ * illustrate:
+ *
+ * and xor dest RGB (1=0xffffff, 0=0x000000)
+ *
+ * dest alpha (1=0xff, 0=0x00)
+ *
+ * 11111 00000 00000 00000
+ * 11111 00000 00000 01110
+ * 11111 00100 => 00100 01110
+ * 11111 00100 00100 01110
+ * 11111 00000 00000 01110
+ * 11111 00000 00000 00000
+ *
+ */
static void mono_cursor(display_cursor *cursor, const guint8 *data)
{
- const guint8 *xor, *and;
+ const guint8 *xor, *xor_base, *and;
guint8 *dest;
int bpl, x, y, bit;
+ bool and_ones = cursor_is_and_ones(cursor, data);
bpl = (cursor->hdr.width + 7) / 8;
and = data;
- xor = and + bpl * cursor->hdr.height;
+ xor_base = xor = and + bpl * cursor->hdr.height;
dest = (uint8_t *)cursor->data;
#ifdef DEBUG_CURSOR
print_cursor(cursor, data);
@@ -291,26 +343,19 @@ static void mono_cursor(display_cursor *cursor, const guint8 *data)
for (y = 0; y < cursor->hdr.height; y++) {
bit = 0x80;
for (x = 0; x < cursor->hdr.width; x++, dest += 4) {
+ if (cursor_is_xor_edge(cursor, xor_base, bpl, x, y) && and_ones) {
+ dest[0] = 0x00;
+ dest[1] = 0x00;
+ dest[2] = 0x00;
+ dest[3] = 0xff;
+ goto next_bit;
+ }
if (and[x/8] & bit) {
if (xor[x/8] & bit) {
- /*
- * flip -> unsupported by x11, since XCreatePixmapCursor has
- * no invert functionality, only a mask, shape, background and
- * foreground colors. Use this checkerboard hack to get some
- * contrast for cursors in the guest that relied on invert for
- * the same contrast.
- */
- if ((x ^ y) & 1) {
- dest[0] = 0xff;
- dest[1] = 0xff;
- dest[2] = 0xff;
- dest[3] = 0xff;
- } else {
- dest[0] = 0x00;
- dest[1] = 0x00;
- dest[2] = 0x00;
- dest[3] = 0x00;
- }
+ dest[0] = 0xff;
+ dest[1] = 0xff;
+ dest[2] = 0xff;
+ dest[3] = 0xff;
} else {
/* unchanged -> transparent */
dest[0] = 0x00;
@@ -333,6 +378,7 @@ static void mono_cursor(display_cursor *cursor, const guint8 *data)
dest[3] = 0xff;
}
}
+ next_bit:
bit >>= 1;
if (bit == 0) {
bit = 0x80;
--
1.8.3.1
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