1 files changed, 60 insertions, 0 deletions
diff --git a/render/matrix.c b/render/matrix.c
index 4de20e5d..c7b11efe 100644
--- a/render/matrix.c
+++ b/render/matrix.c
@@ -1,5 +1,6 @@
 #include <string.h>
 #include <math.h>
+#include <wayland-server-protocol.h>
 #include <wlr/render/matrix.h>
 
 /* Obtains the index for the given row/column */
@@ -81,3 +82,62 @@ void wlr_matrix_mul(const float (*x)[16], const float (*y)[16], float (*product)
 	};
 	memcpy(*product, _product, sizeof(_product));
 }
+
+static const float transforms[][4] = {
+	[WL_OUTPUT_TRANSFORM_NORMAL] = {
+		1.0f, 0.0f,
+		0.0f, -1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_90] = {
+		0.0f, -1.0f,
+		-1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_180] = {
+		-1.0f, 0.0f,
+		0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_270] = {
+		0.0f, 1.0f,
+		1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED] = {
+		-1.0f, 0.0f,
+		0.0f, -1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_90] = {
+		0.0f, 1.0f,
+		-1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_180] = {
+		1.0f, 0.0f,
+		0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_270] = {
+		0.0f, -1.0f,
+		1.0f, 0.0f,
+	},
+};
+
+// Equivilent to glOrtho(0, width, 0, height, 1, -1) with the transform applied
+void wlr_matrix_surface(float mat[static 16], int32_t width, int32_t height,
+		enum wl_output_transform transform) {
+	memset(mat, 0, sizeof(*mat) * 16);
+
+	const float *t = transforms[transform];
+	float x = 2.0f / width;
+	float y = 2.0f / height;
+
+	// Rotation + relection
+	mat[0] = x * t[0];
+	mat[1] = x * t[1];
+	mat[4] = y * t[2];
+	mat[5] = y * t[3];
+
+	// Translation
+	mat[3] = -copysign(1.0f, mat[0] + mat[1]);
+	mat[7] = -copysign(1.0f, mat[4] + mat[5]);
+
+	// Identity
+	mat[10] = 1.0f;
+	mat[15] = 1.0f;
+}