* Fix compiler warnings for nanovg wrapper
Code for the nanovg wrapper was generating compiler warnings for
implicit casts from int32_t to uint16_t. These casts are unavoidable
due to how bgfx and nanovg APIs use different types for texture
width/height.
* Fix compiler warning from nanovg fontstash.h
This fixes some warnings for signed/unsigned comparsion
coming from the nanovg fontstash.h header.
The nvgCreateBgfxTexture() helper function is already implemented in
the nanovg wrapper library, so its useful to expose this function
to the user.
Also expose the NVG_IMAGE_NODELETE flag so this can be passed to the
nvgCreateBgfxTexture() function, to indicate that the caller retains
ownership of the bgfx texture.
This commit changes the `nvgluCreateFramebuffer()` function to not assign a view id automatically as it would easily reach the limit of `uint8_t`. Instead, a new `nvgluSetViewFramebuffer()` function is created to allow users to assign the view id manually as mentioned in #1095.
This commit updates NanoVG's bgfx backend to match the original NanoVG's latest commit, which has significant changes about composite operation implementation as mentioned in pull request https://github.com/memononen/nanovg/pull/312.
This commit updates bgfx's NanoVG codebase to adapt the latest NanoVG commit since I've implemented blending support for the original NanoVG and there is no need of `nvgState()` anymore.
This commit updates nanovg's bgfx backend to adopt premultiplied alpha as the default blending mode just like the original nanovg. Both the fragment shader and the `glnvg__convertPaint()` function are updated to match the original nanovg counterpart.
However, the binary file of the fragment shader is built on Mac so DirectX support is missing.
This commit ports nanovg's helper functions for rendering stuff in framebuffer defined in `nanovg_gl_utils.h`. Also, a new `nvgState()` function is created for bgfx backend so it is possible to blend between framebuffers, which feature is long requested but not yet supported in original nanovg. The `nvgState()` function can be called between `nvgBeginFrame()` and `nvgEndFrame()`.
