add GLES 2 renderer for 2D

This commit adds a new rendering backend, GLES2, and adds a
project setting to enable it.

Currently this backend can only be used on the X11 platform,
but integrating into other platforms is planned.

1 files changed, 141 insertions, 0 deletions

diff --git a/drivers/gles2/shaders/canvas.glsl b/drivers/gles2/shaders/canvas.glsl
new file mode 100644
index 0000000000..11c6ab9b76
--- /dev/null
+++ b/drivers/gles2/shaders/canvas.glsl
@@ -0,0 +1,141 @@
+[vertex]
+
+#ifdef USE_GLES_OVER_GL
+#define mediump
+#define highp
+#else
+precision mediump float;
+precision mediump int;
+#endif
+
+uniform highp mat4 projection_matrix;
+uniform highp mat4 modelview_matrix;
+uniform highp mat4 extra_matrix;
+attribute highp vec2 vertex; // attrib:0
+attribute vec4 color_attrib; // attrib:3
+attribute vec2 uv_attrib; // attrib:4
+
+varying vec2 uv_interp;
+varying vec4 color_interp;
+
+uniform highp vec2 color_texpixel_size;
+
+#ifdef USE_TEXTURE_RECT
+
+uniform vec4 dst_rect;
+uniform vec4 src_rect;
+
+#endif
+
+uniform bool blit_pass;
+
+VERTEX_SHADER_GLOBALS
+
+vec2 select(vec2 a, vec2 b, bvec2 c) {
+	vec2 ret;
+
+	ret.x = c.x ? b.x : a.x;
+	ret.y = c.y ? b.y : a.y;
+
+	return ret;
+}
+
+void main() {
+
+	vec4 color = color_attrib;
+
+#ifdef USE_TEXTURE_RECT
+
+	if (dst_rect.z < 0.0) { // Transpose is encoded as negative dst_rect.z
+		uv_interp = src_rect.xy + abs(src_rect.zw) * vertex.yx;
+	} else {
+		uv_interp = src_rect.xy + abs(src_rect.zw) * vertex;
+	}
+
+	vec4 outvec = vec4(0.0, 0.0, 0.0, 1.0);
+
+	// This is what is done in the GLES 3 bindings and should
+	// take care of flipped rects.
+	//
+	// But it doesn't.
+	// I don't know why, will need to investigate further.
+
+	outvec.xy = dst_rect.xy + abs(dst_rect.zw) * select(vertex, vec2(1.0, 1.0) - vertex, lessThan(src_rect.zw, vec2(0.0, 0.0)));
+
+	// outvec.xy = dst_rect.xy + abs(dst_rect.zw) * vertex;
+#else
+	vec4 outvec = vec4(vertex.xy, 0.0, 1.0);
+
+#ifdef USE_UV_ATTRIBUTE
+	uv_interp = uv_attrib;
+#else
+	uv_interp = vertex.xy;
+#endif
+
+#endif
+
+{
+        vec2 src_vtx=outvec.xy;
+VERTEX_SHADER_CODE
+
+}
+
+	color_interp = color;
+
+	gl_Position = projection_matrix * modelview_matrix * outvec;
+
+}
+
+[fragment]
+
+#ifdef USE_GLES_OVER_GL
+#define mediump
+#define highp
+#else
+precision mediump float;
+precision mediump int;
+#endif
+
+uniform sampler2D color_texture; // texunit:0
+uniform highp vec2 color_texpixel_size;
+uniform mediump sampler2D normal_texture; // texunit:1
+
+varying mediump vec2 uv_interp;
+varying mediump vec4 color_interp;
+
+uniform bool blit_pass;
+
+uniform vec4 final_modulate;
+
+#ifdef SCREEN_TEXTURE_USED
+
+uniform sampler2D screen_texture; // texunit:2
+
+#endif
+
+#ifdef SCREEN_UV_USED
+
+uniform vec2 screen_pixel_size;
+
+#endif
+
+FRAGMENT_SHADER_GLOBALS
+
+
+void main() {
+
+	vec4 color = color_interp;
+
+	color *= texture2D(color_texture, uv_interp);
+{
+
+FRAGMENT_SHADER_CODE
+
+
+}
+
+	color *= final_modulate;
+
+	gl_FragColor = color;
+
+}