These stubs are largely implemented the same: their API is exposed, but
they print to the debug console and sometimes `TODO()`. These changes
allow GLU and Tux Racer to build.
Methods stubbed:
* `glTexImage1D`
* `glTexImage3D`
* `glTexCoord2d(v)`
* `glNormalPointer`
* `glTexGen(d|f|i)`
* `glTexGenfv`
Implement support for the `GL_TEXTURE` matrix mode, the texture matrix
stack and texture coordinate matrix transformation.
Also, an unused `m_current_matrix` was removed to make room for
`m_texture_matrix`.
The `glGet*` family of functions requires that all parameters of
different types are transparently converted into each other. For
example, you can request a boolean parameter as a float or a list of
double values as an integer. It might be considered bad practice to
request parameters through the wrongly-typed function, but to be spec-
compliant we need to implement this.
Introduce a new `::get_context_parameter()` to obtain a parameter
value, which is then converted to the right type by the respective
`::gl_get_*()` functions.
GLES 2.0 is a subset of OpenGL, so we allow applications to compile
against LibGL as if it fully supports GLES 2.0.
Additionally, we set the definitions to an integer value of `1` so
applications that check for availability like this...
int main() { return GL_ES_VERSION_2_0; }
...can actually compile. At least ScummVM uses this, and Mesa defines
their constants in the same way:
44b9e11ddb/include/GL/gl.h (L105)
These enums are used to indicate byte-alignment when reading from and
to textures. The `GL_UNPACK_ROW_LENGTH` value was reimplemented to
support overriding the source data row width.
According to the Khronos group, GL enum values are in the spec:
https://www.khronos.org/registry/OpenGL/docs/enums.html
Not adhering to their values will cause issues with projects that ship
their own copy of `gl.h`, such as ScummVM.
