[FEATURE] simple GUI support

src/shaders/gui_shader.cpp

@@ -0,0 +1,57 @@
+#include "gui_shader.h"
+
+namespace shaders
+{
+	static std::string vertex_shader = R"(
+	#version 140
+
+	in vec2 position;
+
+	out vec2 texture_coords;
+
+	uniform mat4 model_matrix;
+
+	void main(void)
+	{
+		gl_Position = model_matrix * vec4(position, 0.0, 1.0);
+	
+		// This makes top left corner coordinate (0, 0) and bottom right (1, 1)
+		texture_coords = vec2((position.x + 1.0) / 2.0, 1 - (position.y + 1.0) / 2.0);
+	}
+	)";
+
+
+	static std::string fragment_shader = R"(
+	#version 140
+
+	in vec2 texture_coords;
+
+	out vec4 out_color;
+
+	uniform sampler2D gui_texture;
+
+	void main(void)
+	{
+		out_color = texture(gui_texture, texture_coords);
+	}
+	)";
+
+	
+	GuiShader::GuiShader() : ShaderProgram(vertex_shader, fragment_shader)
+	{ }
+
+	void GuiShader::LoadModelMatrix(const glm::mat4& matrix) const
+	{
+		LoadMatrix(location_model_matrix, matrix);
+	}
+
+	void GuiShader::SetAttributes() const
+	{
+		SetAttribute(0, "position");
+	}
+
+	void GuiShader::GetAllUniformLocations()
+	{
+		location_model_matrix = GetUniformLocation("model_matrix");
+	}
+}