Added support for OpenGL 2.1

4 files changed, 84 insertions, 55 deletions

diff --git a/src/Makefile b/src/Makefile
index ce703c3a..33b666b4 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -51,6 +51,7 @@ ifeq ($(PLATFORM),PLATFORM_RPI)
 else
     # define raylib graphics api to use (OpenGL 1.1 by default)
     GRAPHICS ?= GRAPHICS_API_OPENGL_11
+    #GRAPHICS = GRAPHICS_API_OPENGL_21  # Uncomment to use OpenGL 2.1
     #GRAPHICS = GRAPHICS_API_OPENGL_33  # Uncomment to use OpenGL 3.3
 endif
 ifeq ($(PLATFORM),PLATFORM_WEB)
diff --git a/src/core.c b/src/core.c
index fb71af21..7c2dbcb9 100644
--- a/src/core.c
+++ b/src/core.c
@@ -1480,16 +1480,21 @@ static void InitDisplay(int width, int height)
     // NOTE: When asking for an OpenGL context version, most drivers provide highest supported version
     // with forward compatibility to older OpenGL versions.
     // For example, if using OpenGL 1.1, driver can provide a 3.3 context fordward compatible.
-
-    // Check selection OpenGL version (not initialized yet!)
-    if (rlGetVersion() == OPENGL_33)
+    
+    if (configFlags & FLAG_MSAA_4X_HINT)
     {
-        if (configFlags & FLAG_MSAA_4X_HINT)
-        {
-            glfwWindowHint(GLFW_SAMPLES, 4);       // Enables multisampling x4 (MSAA), default is 0
-            TraceLog(INFO, "Trying to enable MSAA x4");
-        }
+        glfwWindowHint(GLFW_SAMPLES, 4);       // Enables multisampling x4 (MSAA), default is 0
+        TraceLog(INFO, "Trying to enable MSAA x4");
+    }
 
+    // Check selection OpenGL version
+    if (rlGetVersion() == OPENGL_21)
+    {
+        glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);        // Choose OpenGL major version (just hint)
+        glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);        // Choose OpenGL minor version (just hint)
+    }
+    else if (rlGetVersion() == OPENGL_33)
+    {
         glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);        // Choose OpenGL major version (just hint)
         glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);        // Choose OpenGL minor version (just hint)
         glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // Profiles Hint: Only 3.3 and above!
diff --git a/src/rlgl.c b/src/rlgl.c
index fec03926..99ef4a4f 100644
--- a/src/rlgl.c
+++ b/src/rlgl.c
@@ -44,6 +44,10 @@
     #endif
 #endif
 
+#if defined(GRAPHICS_API_OPENGL_21)
+    #define GRAPHICS_API_OPENGL_33
+#endif
+
 #if defined(GRAPHICS_API_OPENGL_33)
     #ifdef __APPLE__ 
         #include <OpenGL/gl3.h>     // OpenGL 3 library for OSX
@@ -916,6 +920,8 @@ int rlGetVersion(void)
 {
 #if defined(GRAPHICS_API_OPENGL_11)
     return OPENGL_11;
+#elif defined(GRAPHICS_API_OPENGL_21)
+    return OPENGL_21;
 #elif defined(GRAPHICS_API_OPENGL_33)
     return OPENGL_33;
 #elif defined(GRAPHICS_API_OPENGL_ES2)
@@ -1213,7 +1219,8 @@ void rlglLoadExtensions(void *loader)
     if (!gladLoadGLLoader((GLADloadproc)loader)) TraceLog(WARNING, "GLAD: Cannot load OpenGL extensions");
     else TraceLog(INFO, "GLAD: OpenGL extensions loaded successfully");
 
-    if (GLAD_GL_VERSION_3_3) TraceLog(INFO, "OpenGL 3.3 Core profile supported");
+    if (GLAD_GL_VERSION_2_1) TraceLog(INFO, "OpenGL 2.1 profile supported");
+    else if(GLAD_GL_VERSION_3_3) TraceLog(INFO, "OpenGL 3.3 Core profile supported");
     else TraceLog(ERROR, "OpenGL 3.3 Core profile not supported");
 
     // With GLAD, we can check if an extension is supported using the GLAD_GL_xxx booleans
@@ -2752,55 +2759,65 @@ static Shader LoadDefaultShader(void)
     Shader shader;
 
     // Vertex shader directly defined, no external file required
-#if defined(GRAPHICS_API_OPENGL_33)
-    char vShaderStr[] = "#version 330       \n"
-        "in vec3 vertexPosition;            \n"
-        "in vec2 vertexTexCoord;            \n"
-        "in vec4 vertexColor;               \n"
-        "out vec2 fragTexCoord;             \n"
-        "out vec4 fragColor;                \n"
+    char vDefaultShaderStr[] =
+#if defined(GRAPHICS_API_OPENGL_21)
+    "#version 120                       \n"
 #elif defined(GRAPHICS_API_OPENGL_ES2)
-    char vShaderStr[] = "#version 100       \n"
-        "attribute vec3 vertexPosition;     \n"
-        "attribute vec2 vertexTexCoord;     \n"
-        "attribute vec4 vertexColor;        \n"
-        "varying vec2 fragTexCoord;         \n"
-        "varying vec4 fragColor;            \n"
-#endif
-        "uniform mat4 mvpMatrix;            \n"
-        "void main()                        \n"
-        "{                                  \n"
-        "    fragTexCoord = vertexTexCoord; \n"
-        "    fragColor = vertexColor;       \n"
-        "    gl_Position = mvpMatrix*vec4(vertexPosition, 1.0); \n"
-        "}                                  \n";
+    "#version 100                       \n"
+#endif
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+    "attribute vec3 vertexPosition;     \n"
+    "attribute vec2 vertexTexCoord;     \n"
+    "attribute vec4 vertexColor;        \n"
+    "varying vec2 fragTexCoord;         \n"
+    "varying vec4 fragColor;            \n"
+#elif defined(GRAPHICS_API_OPENGL_33)
+    "#version 330                       \n"
+    "in vec3 vertexPosition;            \n"
+    "in vec2 vertexTexCoord;            \n"
+    "in vec4 vertexColor;               \n"
+    "out vec2 fragTexCoord;             \n"
+    "out vec4 fragColor;                \n"
+#endif
+    "uniform mat4 mvpMatrix;            \n"
+    "void main()                        \n"
+    "{                                  \n"
+    "    fragTexCoord = vertexTexCoord; \n"
+    "    fragColor = vertexColor;       \n"
+    "    gl_Position = mvpMatrix*vec4(vertexPosition, 1.0); \n"
+    "}                                  \n";
 
     // Fragment shader directly defined, no external file required
-#if defined(GRAPHICS_API_OPENGL_33)
-    char fShaderStr[] = "#version 330       \n"
-        "in vec2 fragTexCoord;              \n"
-        "in vec4 fragColor;                 \n"
-        "out vec4 finalColor;               \n"
+    char fDefaultShaderStr[] =
+#if defined(GRAPHICS_API_OPENGL_21)
+    "#version 120                       \n"
 #elif defined(GRAPHICS_API_OPENGL_ES2)
-    char fShaderStr[] = "#version 100       \n"
-        "precision mediump float;           \n"     // precision required for OpenGL ES2 (WebGL)
-        "varying vec2 fragTexCoord;         \n"
-        "varying vec4 fragColor;            \n"
-#endif
-        "uniform sampler2D texture0;        \n"
-        "uniform vec4 colDiffuse;           \n"
-        "void main()                        \n"
-        "{                                  \n"
-#if defined(GRAPHICS_API_OPENGL_33)
-        "    vec4 texelColor = texture(texture0, fragTexCoord);   \n"
-        "    finalColor = texelColor*colDiffuse*fragColor;        \n"
-#elif defined(GRAPHICS_API_OPENGL_ES2)
-        "    vec4 texelColor = texture2D(texture0, fragTexCoord); \n" // NOTE: texture2D() is deprecated on OpenGL 3.3 and ES 3.0
-        "    gl_FragColor = texelColor*colDiffuse*fragColor;      \n"
+    "#version 100                       \n"
+    "precision mediump float;           \n"     // precision required for OpenGL ES2 (WebGL)
+#endif
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+    "varying vec2 fragTexCoord;         \n"
+    "varying vec4 fragColor;            \n"
+#elif defined(GRAPHICS_API_OPENGL_33)
+    "#version 330       \n"
+    "in vec2 fragTexCoord;              \n"
+    "in vec4 fragColor;                 \n"
+    "out vec4 finalColor;               \n"
+#endif
+    "uniform sampler2D texture0;        \n"
+    "uniform vec4 colDiffuse;           \n"
+    "void main()                        \n"
+    "{                                  \n"
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+    "    vec4 texelColor = texture2D(texture0, fragTexCoord); \n" // NOTE: texture2D() is deprecated on OpenGL 3.3 and ES 3.0
+    "    gl_FragColor = texelColor*colDiffuse*fragColor;      \n"
+#elif defined(GRAPHICS_API_OPENGL_33)
+    "    vec4 texelColor = texture(texture0, fragTexCoord);   \n"
+    "    finalColor = texelColor*colDiffuse*fragColor;        \n"
 #endif
-        "}                                  \n";
+    "}                                  \n";
 
-    shader.id = LoadShaderProgram(vShaderStr, fShaderStr);
+    shader.id = LoadShaderProgram(vDefaultShaderStr, fDefaultShaderStr);
 
     if (shader.id != 0) TraceLog(INFO, "[SHDR ID %i] Default shader loaded successfully", shader.id);
     else TraceLog(WARNING, "[SHDR ID %i] Default shader could not be loaded", shader.id);
diff --git a/src/rlgl.h b/src/rlgl.h
index 1e77b771..3322d80c 100644
--- a/src/rlgl.h
+++ b/src/rlgl.h
@@ -52,21 +52,27 @@
 //#define GRAPHICS_API_OPENGL_ES2    // Only available on PLATFORM_ANDROID or PLATFORM_RPI or PLATFORM_WEB
 
 // Security check in case no GRAPHICS_API_OPENGL_* defined
-#if !defined(GRAPHICS_API_OPENGL_11) && !defined(GRAPHICS_API_OPENGL_33) && !defined(GRAPHICS_API_OPENGL_ES2)
+#if !defined(GRAPHICS_API_OPENGL_11) && !defined(GRAPHICS_API_OPENGL_21) && !defined(GRAPHICS_API_OPENGL_33) && !defined(GRAPHICS_API_OPENGL_ES2)
     #define GRAPHICS_API_OPENGL_11
 #endif
 
 // Security check in case multiple GRAPHICS_API_OPENGL_* defined
 #if defined(GRAPHICS_API_OPENGL_11)
+    #if defined(GRAPHICS_API_OPENGL_21)
+        #undef GRAPHICS_API_OPENGL_21
+    #endif
     #if defined(GRAPHICS_API_OPENGL_33)
         #undef GRAPHICS_API_OPENGL_33
     #endif
-
     #if defined(GRAPHICS_API_OPENGL_ES2)
         #undef GRAPHICS_API_OPENGL_ES2
     #endif
 #endif
 
+#if defined(GRAPHICS_API_OPENGL_21)
+    #define GRAPHICS_API_OPENGL_33
+#endif
+
 //----------------------------------------------------------------------------------
 // Defines and Macros
 //----------------------------------------------------------------------------------
@@ -90,7 +96,7 @@ typedef enum { RL_PROJECTION, RL_MODELVIEW, RL_TEXTURE } MatrixMode;
 
 typedef enum { RL_LINES, RL_TRIANGLES, RL_QUADS } DrawMode;
 
-typedef enum { OPENGL_11 = 1, OPENGL_33, OPENGL_ES_20 } GlVersion;
+typedef enum { OPENGL_11 = 1, OPENGL_21, OPENGL_33, OPENGL_ES_20 } GlVersion;
 
 #if defined(RLGL_STANDALONE)
     #ifndef __cplusplus