iOS SDL2 OpenGL ES Cannot Draw Texture - ios

Question

I have been trying to follow the below example but using iOS/Xcode instead of VS2015 (which shows an example of an Android cross-platform project).
Youtube Link
I cannot get the code to display any of my texture at all. No matter what I try I only get a small white rectangle. What am I doing wrong?
This should be OpenGL ES1.x so no shaders should be required.
#import <Foundation/Foundation.h>
#include "SDL.h"
#include <time.h>
#include "SDL_opengles.h"
#define FALSE 0
#define TRUE 1
#ifndef BOOL
#define BOOL int
#endif
#define min(a,b) ((a) < (b) ? (a) : (b))
#define max(a,b) ((a) > (b) ? (a) : (b))
#define SCREEN_WIDTH 320
#define SCREEN_HEIGHT 480
GLuint g_Texture = 0;
BOOL g_Running = TRUE;
SDL_Window *g_SDLWindow = NULL;
SDL_Surface *g_SDLSurface = NULL;
SDL_Renderer *g_SDLRenderer = NULL;
SDL_Texture *g_SDLTexture = NULL;
int g_ScreenHeight = SCREEN_HEIGHT;
int g_ScreenWidth = SCREEN_WIDTH;
unsigned char treeData[420] = {
0x00, 0x00, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x10, 0x00, 0x10, 0x00, 0x20, 0x08, 0x82, 0x00, 0x00, 0x00, 0x00, 0x01,
0x16, 0x1D, 0x38, 0xFF, 0x10, 0x50, 0x6C, 0xFF, 0x83, 0x16, 0x1D, 0x38,
0xFF, 0x00, 0x10, 0x50, 0x6C, 0xFF, 0x82, 0x16, 0x1D, 0x38, 0xFF, 0x82,
0x00, 0x00, 0x00, 0x00, 0x83, 0x00, 0x00, 0x00, 0x00, 0x81, 0x16, 0x1D,
0x38, 0xFF, 0x00, 0x10, 0x50, 0x6C, 0xFF, 0x84, 0x16, 0x1D, 0x38, 0xFF,
0x83, 0x00, 0x00, 0x00, 0x00, 0x85, 0x00, 0x00, 0x00, 0x00, 0x82, 0x16,
0x1D, 0x38, 0xFF, 0x00, 0x10, 0x50, 0x6C, 0xFF, 0x85, 0x00, 0x00, 0x00,
0x00, 0x85, 0x00, 0x00, 0x00, 0x00, 0x01, 0x16, 0x1D, 0x38, 0xFF, 0x10,
0x50, 0x6C, 0xFF, 0x81, 0x16, 0x1D, 0x38, 0xFF, 0x85, 0x00, 0x00, 0x00,
0x00, 0x85, 0x00, 0x00, 0x00, 0x00, 0x83, 0x16, 0x1D, 0x38, 0xFF, 0x85,
0x00, 0x00, 0x00, 0x00, 0x85, 0x00, 0x00, 0x00, 0x00, 0x03, 0x16, 0x1D,
0x38, 0xFF, 0x10, 0x50, 0x6C, 0xFF, 0x16, 0x1D, 0x38, 0xFF, 0x10, 0x50,
0x6C, 0xFF, 0x85, 0x00, 0x00, 0x00, 0x00, 0x82, 0x00, 0x00, 0x00, 0x00,
0x89, 0x24, 0xBA, 0x24, 0xFF, 0x82, 0x00, 0x00, 0x00, 0x00, 0x81, 0x00,
0x00, 0x00, 0x00, 0x87, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x1A, 0x87, 0x2F,
0xFF, 0x82, 0x24, 0xBA, 0x24, 0xFF, 0x81, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x82, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x1A, 0x87,
0x2F, 0xFF, 0x81, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x1A, 0x87, 0x2F, 0xFF,
0x86, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x8F, 0x24,
0xBA, 0x24, 0xFF, 0x81, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x1A, 0x87, 0x2F,
0xFF, 0x86, 0x24, 0xBA, 0x24, 0xFF, 0x05, 0x1A, 0x87, 0x2F, 0xFF, 0x24,
0xBA, 0x24, 0xFF, 0x1A, 0x87, 0x2F, 0xFF, 0x24, 0xBA, 0x24, 0xFF, 0x1A,
0x87, 0x2F, 0xFF, 0x24, 0xBA, 0x24, 0xFF, 0x86, 0x24, 0xBA, 0x24, 0xFF,
0x00, 0x1A, 0x87, 0x2F, 0xFF, 0x87, 0x24, 0xBA, 0x24, 0xFF, 0x81, 0x24,
0xBA, 0x24, 0xFF, 0x02, 0x1A, 0x87, 0x2F, 0xFF, 0x24, 0xBA, 0x24, 0xFF,
0x1A, 0x87, 0x2F, 0xFF, 0x8A, 0x24, 0xBA, 0x24, 0xFF, 0x00, 0x00, 0x00,
0x00, 0x00, 0x88, 0x24, 0xBA, 0x24, 0xFF, 0x02, 0x1A, 0x87, 0x2F, 0xFF,
0x24, 0xBA, 0x24, 0xFF, 0x1A, 0x87, 0x2F, 0xFF, 0x81, 0x24, 0xBA, 0x24,
0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x81, 0x00, 0x00, 0x00, 0x00, 0x84,
0x24, 0xBA, 0x24, 0xFF, 0x00, 0x1A, 0x87, 0x2F, 0xFF, 0x85, 0x24, 0xBA,
0x24, 0xFF, 0x81, 0x00, 0x00, 0x00, 0x00, 0x83, 0x00, 0x00, 0x00, 0x00,
0x87, 0x24, 0xBA, 0x24, 0xFF, 0x83, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x54, 0x52, 0x55, 0x45, 0x56, 0x49,
0x53, 0x49, 0x4F, 0x4E, 0x2D, 0x58, 0x46, 0x49, 0x4C, 0x45, 0x2E, 0x00
};
void LoadTree( void )
{
glGenTextures( 1, &g_Texture );
glBindTexture( GL_TEXTURE_2D, g_Texture );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 16, 16, 0, GL_RGBA, GL_UNSIGNED_BYTE, treeData+18 );
}
//--------------------------------------------------------------------------------------------
// InitSDL()
//--------------------------------------------------------------------------------------------
void InitSDL( void )
{
if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
exit( -1 );
atexit( SDL_Quit );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new*
SDL_DisplayMode currentDisplay;
SDL_GetCurrentDisplayMode( 0, &currentDisplay );
g_ScreenWidth = max( currentDisplay.w, currentDisplay.h );
g_ScreenHeight = min( currentDisplay.w, currentDisplay.h );
SDL_DisplayMode displayMode;
SDL_GetDesktopDisplayMode( 0, &displayMode );
SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES );
// PDS: GLES 2 will require shaders etc..
//SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 2 );
SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 1 );
SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 1 );
g_SDLWindow = SDL_CreateWindow( "Test",
SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED,
g_ScreenWidth,
g_ScreenHeight,
/* SDL_WINDOW_FULLSCFREEN | */ SDL_WINDOW_OPENGL );
if( g_SDLWindow == NULL )
exit( -1 );
SDL_GL_CreateContext( g_SDLWindow );
glViewport( 0, 0, g_ScreenWidth, g_ScreenHeight ); // Reset The Current Viewport
glMatrixMode( GL_PROJECTION ); // Select The Projection Matrix
glLoadIdentity(); // Reset The Projection Matrix
glRotatef( -90, 0, 0, 1 );
glOrthof( 0.0f, g_ScreenWidth, g_ScreenHeight, 0.0f, -1.0f, 1.0f );
glMatrixMode( GL_MODELVIEW ); // Select The Modelview Matrix
glLoadIdentity(); // Reset The Modelview Matrix
glTranslatef(0.5, 0.5, 0);
glClearColor( 0.9f, 0.9f, 0.9f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT );
LoadTree();
glShadeModel(GL_SMOOTH);
}
float sq[] =
{
-7, 7, 0,
7, 7, 0,
-7, -7, 0,
7, -7, 0
};
float tri[] =
{
sq[ 0 ], sq[ 1 ], sq[ 2 ],
sq[ 3 ], sq[ 4 ], sq[ 5 ],
sq[ 6 ], sq[ 7 ], sq[ 8 ],
sq[ 6 ], sq[ 7 ], sq[ 8 ],
sq[ 3 ], sq[ 4 ], sq[ 5 ],
sq[ 9 ], sq[ 10], sq[ 11]
};
float texCoords[]=
{
0, 1,
1, 1,
0, 0,
0, 0,
1, 1,
1, 0
};
//--------------------------------------------------------------------------------------------
// Draw()
//--------------------------------------------------------------------------------------------
void Draw( int x, int y )
{
glEnable( GL_TEXTURE_2D );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glBindTexture( GL_TEXTURE_2D, g_Texture );
glPushMatrix();
glDisable( GL_BLEND );
glDisable( GL_CULL_FACE );
glEnable( GL_TEXTURE_2D );
GLfloat tX = (GLfloat) 10.0f;
GLfloat tY = (GLfloat) 10.0f;
GLfloat xOffset = 0;
GLfloat yOffset = 0;
// PDS: Offset the drawing by half character width since all placement will be done from quad centre..
xOffset = tX;
yOffset = tY;
glTranslatef( xOffset + x, yOffset + y, 0.0f);
glEnableClientState( GL_VERTEX_ARRAY );
glEnableClientState( GL_TEXTURE_COORD_ARRAY );
glFrontFace( GL_CW );
glVertexPointer( 3, GL_FLOAT, 0, tri );
glTexCoordPointer( 2, GL_FLOAT, 0, texCoords );
glDrawArrays( GL_TRIANGLES, 0, 6 );
glDisableClientState( GL_TEXTURE_COORD_ARRAY );
glDisableClientState( GL_VERTEX_ARRAY );
glDisableClientState( GL_COLOR_ARRAY );
glPopMatrix();
glBindTexture( GL_TEXTURE_2D, 0 );
glEnable( GL_BLEND );
}
//--------------------------------------------------------------------------------------------
// main()
//--------------------------------------------------------------------------------------------
int main( int argc, char* argv[] )
{
InitSDL();
SDL_Event event;
while( g_Running )
{
while( SDL_PollEvent( &event ) )
{
switch( event.type )
{
case SDL_QUIT:
g_Running = false;
break;
}
}
Draw( 100, 100 );
SDL_GL_SwapWindow( g_SDLWindow );
}
SDL_Quit();
return EXIT_SUCCESS;
}

Answer 1

I figured this out.. The ordering of setting the Projection and ModelView uniforms was wrong - it had to be done after the shader program was in use.. and I had some crazy vertice values for the triangles making up the destination rectangle.
The raw TGA loading didn't work very well either so I went back to my original code for loading TGA files.
The below link contains a working example.
Working Example