GUAC-236: Add function for copying buffer state.

src/guacenc/buffer.c

@@ -25,6 +25,7 @@
 
 #include <cairo/cairo.h>
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stdlib.h>
 
@@ -141,3 +142,33 @@ int guacenc_buffer_fit(guacenc_buffer* buffer, int x, int y) {
 
 }
 
+int guacenc_buffer_copy(guacenc_buffer* dst, guacenc_buffer* src) {
+
+    /* Resize destination to exactly fit source */
+    if (guacenc_buffer_resize(dst, src->width, src->height))
+        return 1;
+
+    /* Copy surface contents identically */
+    if (src->surface != NULL) {
+
+        /* Destination must be non-NULL as its size is that of the source */
+        assert(dst->cairo != NULL);
+
+        /* Reset state of destination */
+        cairo_t* cairo = dst->cairo;
+        cairo_reset_clip(cairo);
+
+        /* Overwrite destination with contents of source */
+        cairo_set_operator(cairo, CAIRO_OPERATOR_SOURCE);
+        cairo_set_source_surface(cairo, src->surface, 0, 0);
+        cairo_paint(cairo);
+
+        /* Reset operator of destination to default */
+        cairo_set_operator(cairo, CAIRO_OPERATOR_OVER);
+
+    }
+
+    return 0;
+
+}
+

src/guacenc/buffer.h

@@ -136,5 +136,22 @@ int guacenc_buffer_resize(guacenc_buffer* buffer, int width, int height);
  */
 int guacenc_buffer_fit(guacenc_buffer* buffer, int x, int y);
 
+/**
+ * Copies the entire contents of the given source buffer to the destination
+ * buffer, ignoring the current contents of the destination. The destination
+ * buffer's contents are entirely replaced.
+ *
+ * @param dst
+ *     The destination buffer whose contents should be replaced.
+ *
+ * @param src
+ *     The source buffer whose contents should replace those of the destination
+ *     buffer.
+ *
+ * @return
+ *     Zero if the copy operation was successful, non-zero on failure.
+ */
+int guacenc_buffer_copy(guacenc_buffer* dst, guacenc_buffer* src);
+
 #endif