For fixing a previous issue state.canvas_texscreen_used was reset to false at the start of each render_joined_item. This was causing a later shader that used SCREEN_TEXTURE to force recapturing the back buffer immediately prior to use, which we don't want.
This PR preserves the state across joined items, and also prevents joining of items that copy the back buffer as this may be problematic.
It turns out that the original issue that needed the line is now fixed, and the later issue is also fixed by removing it.
While adding more debug checks to legacy renderer, I closed 2 types of vulnerabilities:
* TYPE_PRIMITIVE would previously read from uninitialized data if only specifying a single color
* Other legacy draw operations would fail in debug AFTER accessing out of bounds memory rather than before
Many calls to glBufferSubData are wrapped in a safe version which checks for out of bounds and exits the draw function if this is detected.
Large FVF allows batching of many custom shaders, but should not join items which have shaders that utilize BUILTINs which would change for each item, because these will not be sent individually, and all joined items would wrongly use the values from the first joined item.
Polys that have no texture assigned contain no UVs in the poly command. These were previously not blanked, leading to random values if read from a custom shader.
This PR just blanks them.
In some situations where polygons were scaled, existing software skinning was producing incorrect results.
The transform inverse needed to use an affine inverse rather than a cheaper inverse to account for this scaling.
This adds support for custom shaders for polys, and properly handles modulate in the case of large FVF and modulate FVF.
It also fixes poly vertex colors not being sent to OpenGL.
Antialiased polys work by drawing a smoothed line around the poly after the main drawing. Batching draws polys as a series of triangles with no concept of 'edge', and when 2 polys are joined it becomes impractical to back calculate the edges from the triangles.
For this reason batching is disabled for antialiased polys in this PR.
As a result of the GLES specifications being vague about best practice for how buffers should be used dynamically, different GPUs / platforms appear to have different preferences.
Mac in particular seems to have a number of problems in this area, and none of the rendering team uses Macs. So far we have relied on guesswork to choose the best usage, but in an attempt to pin this down, this PR begins to introduce manual selection of options for users to test their configurations.
Lines are batched using the simplest fvf 'BatchVertex', however when used in an item with a custom shader material, it may attempt to translate to large_fvf without the required extra channels. To prevent this a special case in flushing is made to deal with lines.
In small batches using hardware transform, vertices would be drawn in incorrect positions due to the item transform being applied twice - once in the transform uniform, and once from the transform passed as a vertex attribute.
This PR alters the shader to ignore uniform transforms when using large FVF.
Batching is mostly separated into a common template which can be used with multiple backends (GLES2 and GLES3 here). Only necessary specifics are in the backend files.
Batching is extended to cover more primitives.
