virtio-gpu: replace PIXMAN for region/rect test

Use a simpler implementation for rectangle geometry & intersect, drop
the need for (more complex) PIXMAN functions.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

include/ui/rect.h

@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef QEMU_RECT_H
+#define QEMU_RECT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct QemuRect {
+    int16_t x;
+    int16_t y;
+    uint16_t width;
+    uint16_t height;
+} QemuRect;
+
+static inline void qemu_rect_init(QemuRect *rect,
+                                  int16_t x, int16_t y,
+                                  uint16_t width, uint16_t height)
+{
+    rect->x = x;
+    rect->y = x;
+    rect->width = width;
+    rect->height = height;
+}
+
+static inline void qemu_rect_translate(QemuRect *rect,
+                                       int16_t dx, int16_t dy)
+{
+    rect->x += dx;
+    rect->y += dy;
+}
+
+static inline bool qemu_rect_intersect(const QemuRect *a, const QemuRect *b,
+                                       QemuRect *res)
+{
+    int16_t x1, x2, y1, y2;
+
+    x1 = MAX(a->x, b->x);
+    y1 = MAX(a->y, b->y);
+    x2 = MIN(a->x + a->width, b->x + b->width);
+    y2 = MIN(a->y + a->height, b->y + b->height);
+
+    if (x1 >= x2 || y1 >= y2) {
+        if (res) {
+            qemu_rect_init(res, 0, 0, 0, 0);
+        }
+
+        return false;
+    }
+
+    if (res) {
+        qemu_rect_init(res, x1, y1, x2 - x1, y2 - y1);
+    }
+
+    return true;
+}
+
+#endif