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.
This controls how fetched texels are combined with the color that was
produced by a preceding texture unit or with the vertex color if it is
the first texture unit.
Currently only a small subset of possible combine modes is implemented
as required by glquake.
This sets the length of a row for the image to be transferred. This
value is measured in pixels. When a rectangle with a width less than
this value is transferred the remaining pixels of this row are skipped.
Currently just sets the renderer option for what polygon mode we
want the rasterizer to draw in. GLQuake only uses `GL_FRONT_AND_BACK`
with `GL_FILL` )which implies both back and front facing triangles
are to be filled completely by the rasterizer), so keeping this as
a small stub is perfectly fine for now.
