Fixed the glitch.

trivial-opengl-blit

// Texture: 1024 x 1024 x 4bpp
// Contains 1024 x 768 image from (0,0) to (1024, 768)

// Use glOrtho like glOrtho2d
glOrtho(0, width, height, 0, -1, 1);

// This solved it!
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(0.0, 1.0, 0.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glBindTexture(GL_TEXTURE_2D, display->texture);

GLfloat w = display->source_width / (GLfloat)TEXTURE_SIZE;
GLfloat h = display->source_height / (GLfloat)TEXTURE_SIZE;
GLfloat margin = display->width - display->source_width / 2;
GLfloat box[] = {margin,display->source_height,0, display->source_width,display->source_height,0, margin,0,0, display->source_width,0,0};
GLfloat tex[] = {0,h,   w,h,   0,0,   w,0};

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

glVertexPointer(3, GL_FLOAT, 0, box);
glTexCoordPointer(2, GL_FLOAT, 0, tex);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_2D);