Found another remaining _DEBUG reference

source/glad.c

@@ -1,22 +1,22 @@
 /*
 
-    OpenGL loader generated by glad 0.1.36 on Tue May 14 15:22:23 2024.
+    OpenGL loader generated by glad 0.1.36 on Sun May 26 16:07:25 2024.
 
     Language/Generator: C/C++
     Specification: gl
-    APIs: gl=4.6
+    APIs: gl=4.5
     Profile: core
     Extensions:
-        
+        GL_AMD_vertex_shader_layer
     Loader: True
     Local files: False
     Omit khrplatform: False
     Reproducible: False
 
     Commandline:
-        --profile="core" --api="gl=4.6" --generator="c" --spec="gl" --extensions=""
+        --profile="core" --api="gl=4.5" --generator="c" --spec="gl" --extensions="GL_AMD_vertex_shader_layer"
     Online:
-        https://glad.dav1d.de/#profile=core&language=c&specification=gl&loader=on&api=gl%3D4.6
+        https://glad.dav1d.de/#profile=core&language=c&specification=gl&loader=on&api=gl%3D4.5&extensions=GL_AMD_vertex_shader_layer
 */
 
 #include <stdio.h>
@@ -273,7 +273,6 @@ int GLAD_GL_VERSION_4_2 = 0;
 int GLAD_GL_VERSION_4_3 = 0;
 int GLAD_GL_VERSION_4_4 = 0;
 int GLAD_GL_VERSION_4_5 = 0;
-int GLAD_GL_VERSION_4_6 = 0;
 PFNGLACTIVESHADERPROGRAMPROC glad_glActiveShaderProgram = NULL;
 PFNGLACTIVETEXTUREPROC glad_glActiveTexture = NULL;
 PFNGLATTACHSHADERPROC glad_glAttachShader = NULL;
@@ -635,11 +634,9 @@ PFNGLMEMORYBARRIERBYREGIONPROC glad_glMemoryBarrierByRegion = NULL;
 PFNGLMINSAMPLESHADINGPROC glad_glMinSampleShading = NULL;
 PFNGLMULTIDRAWARRAYSPROC glad_glMultiDrawArrays = NULL;
 PFNGLMULTIDRAWARRAYSINDIRECTPROC glad_glMultiDrawArraysIndirect = NULL;
-PFNGLMULTIDRAWARRAYSINDIRECTCOUNTPROC glad_glMultiDrawArraysIndirectCount = NULL;
 PFNGLMULTIDRAWELEMENTSPROC glad_glMultiDrawElements = NULL;
 PFNGLMULTIDRAWELEMENTSBASEVERTEXPROC glad_glMultiDrawElementsBaseVertex = NULL;
 PFNGLMULTIDRAWELEMENTSINDIRECTPROC glad_glMultiDrawElementsIndirect = NULL;
-PFNGLMULTIDRAWELEMENTSINDIRECTCOUNTPROC glad_glMultiDrawElementsIndirectCount = NULL;
 PFNGLMULTITEXCOORDP1UIPROC glad_glMultiTexCoordP1ui = NULL;
 PFNGLMULTITEXCOORDP1UIVPROC glad_glMultiTexCoordP1uiv = NULL;
 PFNGLMULTITEXCOORDP2UIPROC glad_glMultiTexCoordP2ui = NULL;
@@ -676,7 +673,6 @@ PFNGLPOINTPARAMETERIVPROC glad_glPointParameteriv = NULL;
 PFNGLPOINTSIZEPROC glad_glPointSize = NULL;
 PFNGLPOLYGONMODEPROC glad_glPolygonMode = NULL;
 PFNGLPOLYGONOFFSETPROC glad_glPolygonOffset = NULL;
-PFNGLPOLYGONOFFSETCLAMPPROC glad_glPolygonOffsetClamp = NULL;
 PFNGLPOPDEBUGGROUPPROC glad_glPopDebugGroup = NULL;
 PFNGLPRIMITIVERESTARTINDEXPROC glad_glPrimitiveRestartIndex = NULL;
 PFNGLPROGRAMBINARYPROC glad_glProgramBinary = NULL;
@@ -758,7 +754,6 @@ PFNGLSECONDARYCOLORP3UIVPROC glad_glSecondaryColorP3uiv = NULL;
 PFNGLSHADERBINARYPROC glad_glShaderBinary = NULL;
 PFNGLSHADERSOURCEPROC glad_glShaderSource = NULL;
 PFNGLSHADERSTORAGEBLOCKBINDINGPROC glad_glShaderStorageBlockBinding = NULL;
-PFNGLSPECIALIZESHADERPROC glad_glSpecializeShader = NULL;
 PFNGLSTENCILFUNCPROC glad_glStencilFunc = NULL;
 PFNGLSTENCILFUNCSEPARATEPROC glad_glStencilFuncSeparate = NULL;
 PFNGLSTENCILMASKPROC glad_glStencilMask = NULL;
@@ -973,6 +968,7 @@ PFNGLVIEWPORTARRAYVPROC glad_glViewportArrayv = NULL;
 PFNGLVIEWPORTINDEXEDFPROC glad_glViewportIndexedf = NULL;
 PFNGLVIEWPORTINDEXEDFVPROC glad_glViewportIndexedfv = NULL;
 PFNGLWAITSYNCPROC glad_glWaitSync = NULL;
+int GLAD_GL_AMD_vertex_shader_layer = 0;
 static void load_GL_VERSION_1_0(GLADloadproc load) {
 	if(!GLAD_GL_VERSION_1_0) return;
 	glad_glCullFace = (PFNGLCULLFACEPROC)load("glCullFace");
@@ -1726,16 +1722,9 @@ static void load_GL_VERSION_4_5(GLADloadproc load) {
 	glad_glGetnMinmax = (PFNGLGETNMINMAXPROC)load("glGetnMinmax");
 	glad_glTextureBarrier = (PFNGLTEXTUREBARRIERPROC)load("glTextureBarrier");
 }
-static void load_GL_VERSION_4_6(GLADloadproc load) {
-	if(!GLAD_GL_VERSION_4_6) return;
-	glad_glSpecializeShader = (PFNGLSPECIALIZESHADERPROC)load("glSpecializeShader");
-	glad_glMultiDrawArraysIndirectCount = (PFNGLMULTIDRAWARRAYSINDIRECTCOUNTPROC)load("glMultiDrawArraysIndirectCount");
-	glad_glMultiDrawElementsIndirectCount = (PFNGLMULTIDRAWELEMENTSINDIRECTCOUNTPROC)load("glMultiDrawElementsIndirectCount");
-	glad_glPolygonOffsetClamp = (PFNGLPOLYGONOFFSETCLAMPPROC)load("glPolygonOffsetClamp");
-}
 static int find_extensionsGL(void) {
 	if (!get_exts()) return 0;
-	(void)&has_ext;
+	GLAD_GL_AMD_vertex_shader_layer = has_ext("GL_AMD_vertex_shader_layer");
 	free_exts();
 	return 1;
 }
@@ -1794,10 +1783,9 @@ static void find_coreGL(void) {
 	GLAD_GL_VERSION_4_3 = (major == 4 && minor >= 3) || major > 4;
 	GLAD_GL_VERSION_4_4 = (major == 4 && minor >= 4) || major > 4;
 	GLAD_GL_VERSION_4_5 = (major == 4 && minor >= 5) || major > 4;
-	GLAD_GL_VERSION_4_6 = (major == 4 && minor >= 6) || major > 4;
-	if (GLVersion.major > 4 || (GLVersion.major >= 4 && GLVersion.minor >= 6)) {
+	if (GLVersion.major > 4 || (GLVersion.major >= 4 && GLVersion.minor >= 5)) {
 		max_loaded_major = 4;
-		max_loaded_minor = 6;
+		max_loaded_minor = 5;
 	}
 }
 
@@ -1825,7 +1813,6 @@ int gladLoadGLLoader(GLADloadproc load) {
 	load_GL_VERSION_4_3(load);
 	load_GL_VERSION_4_4(load);
 	load_GL_VERSION_4_5(load);
-	load_GL_VERSION_4_6(load);
 
 	if (!find_extensionsGL()) return 0;
 	return GLVersion.major != 0 || GLVersion.minor != 0;

source/glad/glad.h

@@ -1,22 +1,22 @@
 /*
 
-    OpenGL loader generated by glad 0.1.36 on Tue May 14 15:22:23 2024.
+    OpenGL loader generated by glad 0.1.36 on Sun May 26 16:07:25 2024.
 
     Language/Generator: C/C++
     Specification: gl
-    APIs: gl=4.6
+    APIs: gl=4.5
     Profile: core
     Extensions:
-        
+        GL_AMD_vertex_shader_layer
     Loader: True
     Local files: False
     Omit khrplatform: False
     Reproducible: False
 
     Commandline:
-        --profile="core" --api="gl=4.6" --generator="c" --spec="gl" --extensions=""
+        --profile="core" --api="gl=4.5" --generator="c" --spec="gl" --extensions="GL_AMD_vertex_shader_layer"
     Online:
-        https://glad.dav1d.de/#profile=core&language=c&specification=gl&loader=on&api=gl%3D4.6
+        https://glad.dav1d.de/#profile=core&language=c&specification=gl&loader=on&api=gl%3D4.5&extensions=GL_AMD_vertex_shader_layer
 */
 
 
@@ -1491,28 +1491,6 @@ typedef void (APIENTRY *GLVULKANPROCNV)(void);
 #define GL_MINMAX 0x802E
 #define GL_CONTEXT_RELEASE_BEHAVIOR 0x82FB
 #define GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH 0x82FC
-#define GL_SHADER_BINARY_FORMAT_SPIR_V 0x9551
-#define GL_SPIR_V_BINARY 0x9552
-#define GL_PARAMETER_BUFFER 0x80EE
-#define GL_PARAMETER_BUFFER_BINDING 0x80EF
-#define GL_CONTEXT_FLAG_NO_ERROR_BIT 0x00000008
-#define GL_VERTICES_SUBMITTED 0x82EE
-#define GL_PRIMITIVES_SUBMITTED 0x82EF
-#define GL_VERTEX_SHADER_INVOCATIONS 0x82F0
-#define GL_TESS_CONTROL_SHADER_PATCHES 0x82F1
-#define GL_TESS_EVALUATION_SHADER_INVOCATIONS 0x82F2
-#define GL_GEOMETRY_SHADER_PRIMITIVES_EMITTED 0x82F3
-#define GL_FRAGMENT_SHADER_INVOCATIONS 0x82F4
-#define GL_COMPUTE_SHADER_INVOCATIONS 0x82F5
-#define GL_CLIPPING_INPUT_PRIMITIVES 0x82F6
-#define GL_CLIPPING_OUTPUT_PRIMITIVES 0x82F7
-#define GL_POLYGON_OFFSET_CLAMP 0x8E1B
-#define GL_SPIR_V_EXTENSIONS 0x9553
-#define GL_NUM_SPIR_V_EXTENSIONS 0x9554
-#define GL_TEXTURE_MAX_ANISOTROPY 0x84FE
-#define GL_MAX_TEXTURE_MAX_ANISOTROPY 0x84FF
-#define GL_TRANSFORM_FEEDBACK_OVERFLOW 0x82EC
-#define GL_TRANSFORM_FEEDBACK_STREAM_OVERFLOW 0x82ED
 #ifndef GL_VERSION_1_0
 #define GL_VERSION_1_0 1
 GLAPI int GLAD_GL_VERSION_1_0;
@@ -3670,21 +3648,9 @@ typedef void (APIENTRYP PFNGLTEXTUREBARRIERPROC)(void);
 GLAPI PFNGLTEXTUREBARRIERPROC glad_glTextureBarrier;
 #define glTextureBarrier glad_glTextureBarrier
 #endif
-#ifndef GL_VERSION_4_6
-#define GL_VERSION_4_6 1
-GLAPI int GLAD_GL_VERSION_4_6;
-typedef void (APIENTRYP PFNGLSPECIALIZESHADERPROC)(GLuint shader, const GLchar *pEntryPoint, GLuint numSpecializationConstants, const GLuint *pConstantIndex, const GLuint *pConstantValue);
-GLAPI PFNGLSPECIALIZESHADERPROC glad_glSpecializeShader;
-#define glSpecializeShader glad_glSpecializeShader
-typedef void (APIENTRYP PFNGLMULTIDRAWARRAYSINDIRECTCOUNTPROC)(GLenum mode, const void *indirect, GLintptr drawcount, GLsizei maxdrawcount, GLsizei stride);
-GLAPI PFNGLMULTIDRAWARRAYSINDIRECTCOUNTPROC glad_glMultiDrawArraysIndirectCount;
-#define glMultiDrawArraysIndirectCount glad_glMultiDrawArraysIndirectCount
-typedef void (APIENTRYP PFNGLMULTIDRAWELEMENTSINDIRECTCOUNTPROC)(GLenum mode, GLenum type, const void *indirect, GLintptr drawcount, GLsizei maxdrawcount, GLsizei stride);
-GLAPI PFNGLMULTIDRAWELEMENTSINDIRECTCOUNTPROC glad_glMultiDrawElementsIndirectCount;
-#define glMultiDrawElementsIndirectCount glad_glMultiDrawElementsIndirectCount
-typedef void (APIENTRYP PFNGLPOLYGONOFFSETCLAMPPROC)(GLfloat factor, GLfloat units, GLfloat clamp);
-GLAPI PFNGLPOLYGONOFFSETCLAMPPROC glad_glPolygonOffsetClamp;
-#define glPolygonOffsetClamp glad_glPolygonOffsetClamp
+#ifndef GL_AMD_vertex_shader_layer
+#define GL_AMD_vertex_shader_layer 1
+GLAPI int GLAD_GL_AMD_vertex_shader_layer;
 #endif
 
 #ifdef __cplusplus

source/glerminal-private.h

@@ -7,6 +7,7 @@
 #include <glad/glad.h>
 #include <GLFW/glfw3.h>
 
+#include <iostream>
 #include <fstream>
 #include <stdexcept>
 
@@ -82,7 +83,7 @@ namespace glerminal
 		unsigned int m_sprites[CELL_SIZE * CELL_SIZE * (1 << (8 * sizeof(*m_cells)))];
 		glerminal_main_cb m_main;
 
-#ifdef _DEBUG
+#ifdef GLERMINAL_OPENGL_DEBUG_CONTEXT
 		mutable std::ofstream m_log;
 		void log(GLenum type, GLuint id, GLenum severity, const char* message) const;
 #endif

source/glerminal.cpp

@@ -25,8 +25,8 @@ namespace
 		-1,  0 // top left
 	};
 
-	constexpr char* VERTEX_SHADER_SOURCE =
-		"#version 460 core\n"
+	constexpr char VERTEX_SHADER_SOURCE[] =
+		"#version 450 core\n"
 		"layout (location = 0) in vec2 position;\n"
 		"layout (location = 1) in vec2 offset;\n"
 		"layout (location = 2) in int sprite;\n"
@@ -36,7 +36,6 @@ namespace
 		"	float scales[];\n"
 		"} lss;\n"
 		"out VS_OUT {\n"
-		"	flat vec2 offset;\n"
 		"	flat int sprite;\n"
 		"	flat int layer;\n"
 		"	vec2 texcoord;\n"
@@ -44,21 +43,51 @@ namespace
 		"void main()\n"
 		"{\n"
 		"	const int layer = int(floor(gl_InstanceID / " GRID_SIZE_UNIFORM_NAME ".y));\n"
+		"	vec2 scaled_offset = 2 * offset * " GRID_SIZE_UNIFORM_NAME ".zw;\n"
 		"	vs_out.sprite = sprite;\n"
-		"	vs_out.offset = offset * " GRID_SIZE_UNIFORM_NAME ".zw;\n"
 		"	vs_out.layer = layer;\n"
 		"	vs_out.texcoord = vec2(position.x + 1, -position.y);\n"
 		"	vec2 cell_position = vec2(lss.scales[layer] + (gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) - " GRID_SIZE_UNIFORM_NAME ".x * floor((gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) * " GRID_SIZE_UNIFORM_NAME ".z), -floor((gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) * " GRID_SIZE_UNIFORM_NAME ".z));\n"
 		"	vec2 temp = ((position + vec2(-0.5, 0.5)) * lss.scales[layer] + cell_position + vec2(0.5, -0.5)) * " GRID_SIZE_UNIFORM_NAME ".zw * 2 + vec2(-1, 1);\n"
-		"	gl_Position = vec4(temp.x, -temp.y, 0, 1);\n"
+		"	gl_Position = vec4(scaled_offset.x + temp.x, scaled_offset.y - temp.y, 0, 1);\n"
 		"}";
 
-	constexpr char* GEOMETRY_SHADER_SOURCE =
-		"#version 460 core\n"
+	// note: AMD_vertex_shader_layer support required
+	constexpr char VERTEX_SHADER_AMD_SOURCE[] =
+		"#version 450 core\n"
+		"#extension GL_AMD_vertex_shader_layer : enable\n"
+		"layout (location = 0) in vec2 position;\n"
+		"layout (location = 1) in vec2 offset;\n"
+		"layout (location = 2) in int sprite;\n"
+		"uniform vec4 " GRID_SIZE_UNIFORM_NAME ";\n"
+		"layout (std430, binding = 0) buffer LayerScales"
+		"{\n"
+		"	float scales[];\n"
+		"} lss;\n"
+		"out VS_OUT {\n"
+		"	flat int sprite;\n"
+		"	vec2 texcoord;\n"
+		"} vs_out;\n"
+		"void main()\n"
+		"{\n"
+		"	const int layer = int(floor(gl_InstanceID / " GRID_SIZE_UNIFORM_NAME ".y));\n"
+		"	gl_Layer = layer;\n"
+		"	vec2 scaled_offset = 2 * offset * " GRID_SIZE_UNIFORM_NAME ".zw;\n"
+		"	vs_out.sprite = sprite;\n"
+		"	vs_out.texcoord = vec2(position.x + 1, -position.y);\n"
+		"	vec2 cell_position = vec2(lss.scales[layer] + (gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) - " GRID_SIZE_UNIFORM_NAME ".x * floor((gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) * " GRID_SIZE_UNIFORM_NAME ".z), -floor((gl_InstanceID % int(" GRID_SIZE_UNIFORM_NAME ".y)) * " GRID_SIZE_UNIFORM_NAME ".z));\n"
+		"	vec2 temp = ((position + vec2(-0.5, 0.5)) * lss.scales[layer] + cell_position + vec2(0.5, -0.5)) * " GRID_SIZE_UNIFORM_NAME ".zw * 2 + vec2(-1, 1);\n"
+		"	gl_Position = vec4(scaled_offset.x + temp.x, scaled_offset.y - temp.y, 0, 1);\n"
+		"}";
+
+	constexpr const char* VERTEX_SHADER_SOURCE_PTR = VERTEX_SHADER_SOURCE;
+	constexpr const char* VERTEX_SHADER_AMD_SOURCE_PTR = VERTEX_SHADER_AMD_SOURCE;
+
+	constexpr char GEOMETRY_SHADER_SOURCE[] =
+		"#version 450 core\n"
 		"layout (triangles) in;\n"
 		"layout (triangle_strip, max_vertices = 3) out;\n"
 		"in VS_OUT {\n"
-		"   flat vec2 offset;\n"
 		"	flat int sprite;\n"
 		"	flat int layer;\n"
 		"	vec2 texcoord;\n"
@@ -68,25 +97,27 @@ namespace
 		"void main()\n"
 		"{\n"
 		"	gl_Layer = gs_in[0].layer;\n"
-		"	gl_Position = vec4(gl_in[0].gl_Position.xy + gs_in[0].offset * 2, 0, 1);\n"
+		"	gl_Position = gl_in[0].gl_Position;\n"
 		"	sprite = gs_in[0].sprite;\n"
 		"	texcoord = gs_in[0].texcoord;\n"
 		"	EmitVertex();\n"
 		"	gl_Layer = gs_in[1].layer;\n"
-		"	gl_Position = vec4(gl_in[1].gl_Position.xy + gs_in[1].offset * 2, 0, 1);\n"
+		"	gl_Position = gl_in[1].gl_Position;\n"
 		"	sprite = gs_in[1].sprite;\n"
 		"	texcoord = gs_in[1].texcoord;\n"
 		"	EmitVertex();\n"
 		"	gl_Layer = gs_in[2].layer;\n"
-		"	gl_Position = vec4(gl_in[2].gl_Position.xy + gs_in[2].offset * 2, 0, 1);\n"
+		"	gl_Position = gl_in[2].gl_Position;\n"
 		"	sprite = gs_in[2].sprite;\n"
 		"	texcoord = gs_in[2].texcoord;\n"
 		"	EmitVertex();\n"
 		"	EndPrimitive();\n"
 		"}";
 
-	constexpr char* FRAGMENT_SHADER_SOURCE =
-		"#version 460 core\n"
+	constexpr const char* GEOMETRY_SHADER_SOURCE_PTR = GEOMETRY_SHADER_SOURCE;
+
+	constexpr char FRAGMENT_SHADER_SOURCE[] =
+		"#version 450 core\n"
 		"in vec2 texcoord;\n"
 		"flat in int sprite;\n"
 		"layout (binding = 0) uniform sampler2DArray " SPRITES_UNIFORM_NAME ";\n"
@@ -96,8 +127,25 @@ namespace
 		"	FragColor = texture(" SPRITES_UNIFORM_NAME ", vec3(texcoord, sprite));\n"
 		"}";
 
-	constexpr char* SCREEN_VERTEX_SHADER_SOURCE =
-		"#version 460 core\n"
+	// note: AMD_vertex_shader_layer support required
+	constexpr char FRAGMENT_SHADER_AMD_SOURCE[] =
+		"#version 450 core\n"
+		"in VS_OUT {\n"
+		"	flat int sprite;\n"
+		"	vec2 texcoord;\n"
+		"} fs_in;\n"
+		"layout (binding = 0) uniform sampler2DArray " SPRITES_UNIFORM_NAME ";\n"
+		"out vec4 FragColor;\n"
+		"void main()\n"
+		"{\n"
+		"	FragColor = texture(" SPRITES_UNIFORM_NAME ", vec3(fs_in.texcoord, fs_in.sprite));\n"
+		"}";
+
+	constexpr const char* FRAGMENT_SHADER_SOURCE_PTR = FRAGMENT_SHADER_SOURCE;
+	constexpr const char* FRAGMENT_SHADER_AMD_SOURCE_PTR = FRAGMENT_SHADER_AMD_SOURCE;
+
+	constexpr char SCREEN_VERTEX_SHADER_SOURCE[] =
+		"#version 450 core\n"
 		"layout (location = 0) in vec2 position;\n"
 		"out vec2 texcoord;\n"
 		"void main()\n"
@@ -106,8 +154,10 @@ namespace
 		"	texcoord = vec2(position.x + 1, -position.y);\n"
 		"}";
 
+	constexpr const char* SCREEN_VERTEX_SHADER_SOURCE_PTR = SCREEN_VERTEX_SHADER_SOURCE;
+
 	constexpr char* SCREEN_FRAGMENT_SHADER_SOURCE =
-		"#version 460 core\n"
+		"#version 450 core\n"
 		"in vec2 texcoord;\n"
 		"layout (binding = 1) uniform sampler2DArray " LAYERS_UNIFORM_NAME ";\n"
 		"layout (std430, binding = 1) buffer LayerColors"
@@ -126,6 +176,8 @@ namespace
 		"	}\n"
 		"	FragColor = vec4(current_color, 1);\n"
 		"}";
+
+	constexpr const char* SCREEN_FRAGMENT_SHADER_SOURCE_PTR = SCREEN_FRAGMENT_SHADER_SOURCE;
 }
 
 namespace glerminal
@@ -137,7 +189,7 @@ namespace glerminal
 		m_sprites{ },
 		m_layer_colors{ },
 		m_layer_scales{ }
-#ifdef _DEBUG
+#ifdef GLERMINAL_OPENGL_DEBUG_CONTEXT
 		, m_log("log.txt")
 #endif
 	{
@@ -207,14 +259,12 @@ namespace glerminal
 		update_layer_colors();
 		update_layer_scales();
 
-		glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
 		glUseProgram(m_program);
 		glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);
 		glBindVertexArray(m_vao);
 		glClear(GL_COLOR_BUFFER_BIT);
 		glDrawArraysInstanced(GL_TRIANGLES, 0, 6, GRID_AREA * LAYER_COUNT);
 
-		glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
 		glUseProgram(m_screen_program);
 		glBindFramebuffer(GL_FRAMEBUFFER, 0);
 		glBindVertexArray(m_screen_vao);
@@ -293,7 +343,7 @@ namespace glerminal
 		glfwInit();
 
 		glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
-		glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
+		glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 5);
 		glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 		// not resizable for now.
 		// 
@@ -391,6 +441,7 @@ namespace glerminal
 		glDisable(GL_DEPTH_TEST);
 		glEnable(GL_BLEND);
 		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+		glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
 
 		// -- setup vertex data --
 		// create vertex buffer object
@@ -442,17 +493,20 @@ namespace glerminal
 		glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, m_layer_colors_buffer);
 
 		// -- setup shader program --
+		// test for features
+		const bool vertex_shader_layer_supported = glfwExtensionSupported("GL_AMD_vertex_shader_layer");
+
 		// compile
 		const unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
-		glShaderSource(vertex_shader, 1, &VERTEX_SHADER_SOURCE, nullptr);
+		glShaderSource(vertex_shader, 1, &(vertex_shader_layer_supported ? VERTEX_SHADER_AMD_SOURCE_PTR : VERTEX_SHADER_SOURCE_PTR), nullptr);
 		glCompileShader(vertex_shader);
 
 		const unsigned int geometry_shader = glCreateShader(GL_GEOMETRY_SHADER);
-		glShaderSource(geometry_shader, 1, &GEOMETRY_SHADER_SOURCE, nullptr);
+		glShaderSource(geometry_shader, 1, &GEOMETRY_SHADER_SOURCE_PTR, nullptr);
 		glCompileShader(geometry_shader);
 
 		const unsigned int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
-		glShaderSource(fragment_shader, 1, &FRAGMENT_SHADER_SOURCE, nullptr);
+		glShaderSource(fragment_shader, 1, &(vertex_shader_layer_supported ? FRAGMENT_SHADER_AMD_SOURCE_PTR : FRAGMENT_SHADER_SOURCE_PTR), nullptr);
 		glCompileShader(fragment_shader);
 
 		constexpr int INFO_LOG_SIZE = 512;
@@ -499,7 +553,11 @@ namespace glerminal
 		// link
 		m_program = glCreateProgram();
 		glAttachShader(m_program, vertex_shader);
-		glAttachShader(m_program, geometry_shader);
+		// only need geometry shader if AMD_vertex_shader_layer is not supported
+		if (!vertex_shader_layer_supported)
+		{
+			glAttachShader(m_program, geometry_shader);
+		}
 		glAttachShader(m_program, fragment_shader);
 		glLinkProgram(m_program);
 		glDeleteShader(vertex_shader);
@@ -510,6 +568,8 @@ namespace glerminal
 		glGetProgramiv(m_program, GL_LINK_STATUS, &success);
 		if (!success)
 		{
+			glGetProgramInfoLog(m_program, INFO_LOG_SIZE, nullptr, info_log);
+
 			glDeleteProgram(m_program);
 
 			throw std::runtime_error("Could not link shader program.");
@@ -523,11 +583,11 @@ namespace glerminal
 
 		// compile
 		const unsigned int screen_vertex_shader = glCreateShader(GL_VERTEX_SHADER);
-		glShaderSource(screen_vertex_shader, 1, &SCREEN_VERTEX_SHADER_SOURCE, nullptr);
+		glShaderSource(screen_vertex_shader, 1, &SCREEN_VERTEX_SHADER_SOURCE_PTR, nullptr);
 		glCompileShader(screen_vertex_shader);
 
 		const unsigned int screen_fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
-		glShaderSource(screen_fragment_shader, 1, &SCREEN_FRAGMENT_SHADER_SOURCE, nullptr);
+		glShaderSource(screen_fragment_shader, 1, &SCREEN_FRAGMENT_SHADER_SOURCE_PTR, nullptr);
 		glCompileShader(screen_fragment_shader);
 
 		// verify compile
@@ -665,7 +725,7 @@ void glerminal_run(glerminal_init_cb init, glerminal_main_cb main)
 	}
 	catch (const std::runtime_error& e)
 	{
-		e.what();
+		std::cout << e.what() << std::endl;
 	}
 }