Add transform utility functions from wayvnc

include/transform-util.h

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+/*
+ * Copyright (c) 2020 - 2021 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+#include "neatvnc.h"
+
+#include <pixman.h>
+
+void nvnc_transform_to_pixman_transform(pixman_transform_t* dst,
+		enum nvnc_transform src, int width, int height);

src/transform-util.c

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+/*
+ * Copyright (c) 2020 - 2021 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "neatvnc.h"
+
+#include <stdlib.h>
+#include <pixman.h>
+
+/* Note: This function yields the inverse pixman transform of the
+ * nvnc_transform.
+ */
+void nvnc_transform_to_pixman_transform(pixman_transform_t* dst,
+		enum nvnc_transform src, int width, int height)
+{
+#define F1 pixman_fixed_1
+	switch (src) {
+	case NVNC_TRANSFORM_NORMAL:
+		{
+			pixman_transform_t t = {{
+				{ F1, 0, 0 },
+				{ 0, F1, 0 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_90:
+		{
+			pixman_transform_t t = {{
+				{ 0, F1, 0 },
+				{ -F1, 0, height * F1 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_180:
+		{
+			pixman_transform_t t = {{
+				{ -F1, 0, width * F1 },
+				{ 0, -F1, height * F1 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_270:
+		{
+			pixman_transform_t t = {{
+				{ 0, -F1, width * F1 },
+				{ F1, 0, 0 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_FLIPPED:
+		{
+			pixman_transform_t t = {{
+				{ -F1, 0, width * F1 },
+				{ 0, F1, 0 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_FLIPPED_90:
+		{
+			pixman_transform_t t = {{
+				{ 0, F1, 0 },
+				{ F1, 0, 0 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_FLIPPED_180:
+		{
+			pixman_transform_t t = {{
+				{ F1, 0, 0 },
+				{ 0, -F1, height * F1 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	case NVNC_TRANSFORM_FLIPPED_270:
+		{
+			pixman_transform_t t = {{
+				{ 0, -F1, width * F1 },
+				{ -F1, 0, height * F1 },
+				{ 0, 0, F1 },
+			}};
+			*dst = t;
+		}
+		return;
+	}
+#undef F1
+
+	abort();
+}