gg: fix of issue ##21610

[hedgeg0d]

Adding fontstash buffer cleanup when processing resize event. Increasing buffer size to 2048x2048.

_{Huly®: V_0.6-21394}

[spytheman]

Why should that happen on every resize event, and not just once?

[hedgeg0d]

because the font size may change after every resize event

[spytheman]

It may as well not change too - that is specific to the user code.
examples/gg/minimal.v for example or examples/gg/raycaster.v, do not scale their fonts on each resize event.

I think that calling that indiscriminately, while the user drags the border of the window will be too slow for no good benefit 🤔 .

[spytheman]

I think that a better approach would be to use this:

pub fn (s &Context) set_error_callback(callback fn (voidptr, int, int), uptr voidptr) {
    C.fonsSetErrorCallback(s, callback, uptr)
}

so that we can hook into the situations, where the atlas becomes unusable, and reset it only in those cases.

[hedgeg0d]

It seems to me that the window size does not change so often that it somehow significantly affects performance, but this bug really makes itself felt in applications where a lot of labels are rendered at the same time, especially in large font (the buffer stores pixels, so the larger the font, the faster it overflows). But if this is important, maybe it's worth just increasing the buffer size without clearing it?

[spytheman]

Try for example v run examples/gg/minimal.v on master and on this PR to see the effect (while resizing with dragging the border slowly).

[hedgeg0d]

Sorry, i don't know how to cast voidptr to C.FONScontext. How do I do this?

pub fn (s &C.FONScontext) set_error_callback(callback fn (voidptr, int, int), uptr voidptr) {
    C.fonsSetErrorCallback(s, callback, uptr)
}

pub fn clear_atlas_callback(uptr voidptr, error int, val int) {
	ft := C.FONScontext{uptr} // doesn't work
	fons := ft.fons
	C.fonsResetAtlas(fons, 512, 512)
}

[StunxFS]

Sorry, i don't know how to cast voidptr to C.FONScontext. How do I do this?

pub fn (s &C.FONScontext) set_error_callback(callback fn (voidptr, int, int), uptr voidptr) {
    C.fonsSetErrorCallback(s, callback, uptr)
}

pub fn clear_atlas_callback(uptr voidptr, error int, val int) {
	ft := C.FONScontext{uptr} // doesn't work
	fons := ft.fons
	C.fonsResetAtlas(fons, 512, 512)
}

&C.FONScontext(uptr)

[hedgeg0d]

Ok, I made a callback to clear the buffer when it's full, but now I'm getting messages from sokol:

sokol.memory.slog | user_data: (nil), const_tag: sg, level: 0, item_id: 298, fname: sokol_gfx.h, line: 16102, message: VALIDATION_FAILED: validation layer checks failed
sokol.memory.slog | user_data: (nil), const_tag: sg, level: 1, item_id: 270, fname: sokol_gfx.h, line: 16874, message: VALIDATE_ABND_FS_IMG_EXISTS: sg_apply_bindings: image bound to fragment stage no longer alive
sokol.memory.slog | user_data: (nil), const_tag: sg, level: 0, item_id: 298, fname: sokol_gfx.h, line: 16102, message: VALIDATION_FAILED: validation layer checks failed
sokol.memory.slog | user_data: (nil), const_tag: sg, level: 1, item_id: 270, fname: sokol_gfx.h, line: 16874, message: VALIDATE_ABND_FS_IMG_EXISTS: sg_apply_bindings: image bound to fragment stage no longer alive
sokol.memory.slog | user_data: (nil), const_tag: sg, level: 0, item_id: 298, fname: sokol_gfx.h, line: 16102, message: VALIDATION_FAILED: validation layer checks failed

Code(vlib/gg/text_rendering.c.v):

pub fn (s &C.FONScontext) set_error_callback(callback fn (voidptr, int, int), uptr voidptr) {
    C.fonsSetErrorCallback(s, callback, uptr)
}

pub fn clear_atlas_callback(uptr voidptr, error int, val int) {
	if error == 1 { // atlas overflow error code
		fons := unsafe{&fontstash.Context(uptr)}
		C.fonsResetAtlas(fons, buff_size, buff_size)
	}
}

fn new_ft(c FTConfig) ?&FT {
    ...
    ft := &FT{
		fons:        fons
		font_normal: fons.add_font_mem('sans', bytes, false)
		font_bold:   fons.add_font_mem('sans', bytes_bold, false)
		font_mono:   fons.add_font_mem('sans', bytes_mono, false)
		font_italic: fons.add_font_mem('sans', bytes_italic, false)
		scale:       c.scale
    }
    fons.set_error_callback(clear_atlas_callback, fons)
    return ft
}

But apps works just fine

[hedgeg0d]

the effect of resizing the window in v run examples/gg/minimal.v is gone