channel-cursor: mono cursors edge highlighting

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.

Moving the core function to spice-util for testing.

1 files changed, 117 insertions, 0 deletions

diff --git a/tests/util.c b/tests/util.c
index 86109aa..922818a 100644
--- a/tests/util.c
+++ b/tests/util.c
@@ -78,12 +78,129 @@ static void test_unix2dos(void)
     }
 }
 
+static const struct {
+    unsigned width;
+    unsigned height;
+    guint8 *and;
+    guint8 *xor;
+    guint8 *dest;
+} mono[] = {
+    {
+        8, 6,
+        "11111111"
+        "11111111"
+        "11111111"
+        "11111111"
+        "11111111"
+        "11111111"
+        ,
+        "00000000"
+        "00000000"
+        "00000100"
+        "00000100"
+        "00000000"
+        "00000000"
+        ,
+        "0000" "0000" "0000" "0000" "0000" "0000" "0000" "0000"
+        "0000" "0000" "0000" "0000" "0001" "0001" "0001" "0000"
+        "0000" "0000" "0000" "0000" "0001" "1111" "0001" "0000"
+        "0000" "0000" "0000" "0000" "0001" "1111" "0001" "0000"
+        "0000" "0000" "0000" "0000" "0001" "0001" "0001" "0000"
+        "0000" "0000" "0000" "0000" "0000" "0000" "0000" "0000"
+    }
+};
+
+static void set_bit(guint8 *d, unsigned bit, unsigned value)
+{
+    if (value) {
+        *d |= (0x80 >> bit);
+    } else {
+        *d &= ~(0x80 >> bit);
+    }
+}
+
+static void test_set_bit(void)
+{
+    struct {
+        unsigned len;
+        guint8 *src;
+        guint8 *dest;
+    } tests[] = {
+        {
+            4,
+            "1111",
+            "\xf0",
+        },
+        {
+            16,
+            "1111011100110001",
+            "\xf7\x31",
+        }
+    };
+    int i, j, bit;
+    guint8 *dest;
+    int bytes;
+    
+    for (i = 0 ; i < G_N_ELEMENTS(tests); ++i) {
+        bytes = (tests[i].len + 7) / 8;
+        dest = g_malloc0(bytes);
+        for (j = 0 ; j < tests[i].len;) {
+            for (bit = 0 ; bit < 8 && j < tests[i].len; ++bit, ++j) {
+                set_bit(&dest[j / 8], bit, tests[i].src[j] == '0' ? 0 : 1);
+            }
+        }
+        for (j = 0 ; j < bytes; ++j) {
+            g_assert(dest[j] == tests[i].dest[j]);
+        }
+        g_free(dest);
+    }
+}
+
+static void test_mono_edge_highlight(void)
+{
+    int i, j, bit;
+    guint8 *and;
+    guint8 *xor;
+    guint8 *dest;
+    guint8 *dest_correct;
+    int size, pixels;
+
+    test_set_bit();
+
+    for (i = 0 ; i < G_N_ELEMENTS(mono); ++i) {
+        pixels = mono[i].width * mono[i].height;
+        size = (pixels + 7) / 8;
+        and = g_malloc0(size);
+        xor = g_malloc0(size);
+        dest = g_malloc0(pixels * 4);
+        dest_correct = g_malloc(pixels * 4);
+        for (j = 0 ; j < pixels;) {
+            for (bit = 0; bit < 8 && j < pixels; ++bit, ++j) {
+                set_bit(&and[j / 8], bit, mono[i].and[j] == '0' ? 0 : 1);
+                set_bit(&xor[j / 8], bit, mono[i].xor[j] == '0' ? 0 : 1);
+            }
+        }
+        for (j = 0 ; j < pixels * 4 ; ++j) {
+            dest_correct[j] = mono[i].dest[j] == '0' ? 0x00 : 0xff;
+        }
+        spice_mono_edge_highlight(mono[i].width, mono[i].height, and, xor, dest);
+        for (j = 0; j < pixels; ++j) {
+            g_assert(dest[j] == dest_correct[j]);
+        }
+        g_free(and);
+        g_free(xor);
+        g_free(dest);
+        g_free(dest_correct);
+    }
+}
+
 int main(int argc, char* argv[])
 {
   g_test_init(&argc, &argv, NULL);
 
   g_test_add_func("/util/dos2unix", test_dos2unix);
   g_test_add_func("/util/unix2dos", test_unix2dos);
+  g_test_add_func("/util/mono_edge_highlight", test_mono_edge_highlight);
 
   return g_test_run ();
 }