text_renderer: clear VkImage before growing, implement island padding in texture atlas (fix graphical artifacts)

wgui/src/renderer_vk/text/text_atlas.rs

@@ -1,5 +1,5 @@
 use cosmic_text::{FontSystem, SwashCache};
-use etagere::{size2, Allocation, BucketedAtlasAllocator};
+use etagere::{Allocation, BucketedAtlasAllocator, size2};
 use lru::LruCache;
 use rustc_hash::FxHasher;
 use std::{collections::HashSet, hash::BuildHasherDefault, sync::Arc};
@@ -8,20 +8,20 @@ use vulkano::{
 	command_buffer::CommandBufferUsage,
 	descriptor_set::DescriptorSet,
 	format::Format,
-	image::{view::ImageView, Image, ImageCreateInfo, ImageType, ImageUsage},
+	image::{Image, ImageCreateInfo, ImageType, ImageUsage, view::ImageView},
 	memory::allocator::AllocationCreateInfo,
 	pipeline::graphics::vertex_input::Vertex,
 };
 
 use super::{
+	GlyphDetails, GpuCacheStatus,
 	custom_glyph::ContentType,
 	shaders::{frag_atlas, vert_atlas},
 	text_renderer::GlyphonCacheKey,
-	GlyphDetails, GpuCacheStatus,
 };
 use crate::gfx::{
+	BLEND_ALPHA, WGfx,
 	pipeline::{WGfxPipeline, WPipelineCreateInfo},
-	WGfx, BLEND_ALPHA,
 };
 
 /// Pipeline & shaders to be reused between `TextRenderer` instances
@@ -77,6 +77,8 @@ pub(super) struct InnerAtlas {
 	common: TextPipeline,
 }
 
+pub const TEXT_ATLAS_ISLAND_PADDING_PX: u32 = 1;
+
 impl InnerAtlas {
 	const INITIAL_SIZE: u32 = 256;
 
@@ -131,10 +133,15 @@ impl InnerAtlas {
 	}
 
 	pub(super) fn try_allocate(&mut self, width: usize, height: usize) -> Option<Allocation> {
-		let size = size2(width as i32, height as i32);
+		let glyph_size = size2(width as i32, height as i32);
+		let padded_size = glyph_size
+			+ size2(
+				(TEXT_ATLAS_ISLAND_PADDING_PX * 2) as i32,
+				(TEXT_ATLAS_ISLAND_PADDING_PX * 2) as i32,
+			);
 
 		loop {
-			let allocation = self.packer.allocate(size);
+			let allocation = self.packer.allocate(padded_size);
 
 			if allocation.is_some() {
 				return allocation;
@@ -200,6 +207,9 @@ impl InnerAtlas {
 			.gfx
 			.create_xfer_command_buffer(CommandBufferUsage::OneTimeSubmit)?;
 
+		// clear newly allocated image with zeros
+		cmd_buf.clear_image(&image)?;
+
 		// Re-upload glyphs
 		for (&cache_key, glyph) in &self.glyph_cache {
 			let (x, y) = match glyph.gpu_cache {

wgui/src/renderer_vk/text/text_renderer.rs

@@ -1,14 +1,15 @@
 use crate::{
 	gfx::{cmd::GfxCommandBuffer, pass::WGfxPass},
-	renderer_vk::{model_buffer::ModelBuffer, viewport::Viewport},
+	renderer_vk::{model_buffer::ModelBuffer, text::text_atlas::TEXT_ATLAS_ISLAND_PADDING_PX, viewport::Viewport},
 };
 
 use super::{
+	ContentType, FontSystem, GlyphDetails, GpuCacheStatus, SwashCache, TextArea,
 	custom_glyph::{CustomGlyphCacheKey, RasterizeCustomGlyphRequest, RasterizedCustomGlyph},
 	text_atlas::{GlyphVertex, TextAtlas, TextPipeline},
-	ContentType, FontSystem, GlyphDetails, GpuCacheStatus, SwashCache, TextArea,
 };
 use cosmic_text::{Color, SubpixelBin, SwashContent};
+use etagere::size2;
 use glam::{Mat4, Vec2, Vec3};
 use vulkano::{
 	buffer::{BufferUsage, Subbuffer},
@@ -359,14 +360,29 @@ fn prepare_glyph(
 
 				inner = par.atlas.inner_for_content_mut(image.content_type);
 			};
-			let atlas_min = allocation.rectangle.min;
+
+			let atlas_with_island_min = allocation.rectangle.min;
+			let size_with_island = allocation.rectangle.size();
+			let atlas_glyph_min =
+				allocation.rectangle.min + size2(TEXT_ATLAS_ISLAND_PADDING_PX as i32, TEXT_ATLAS_ISLAND_PADDING_PX as i32);
 
 			let mut cmd_buf = gfx.create_xfer_command_buffer(CommandBufferUsage::OneTimeSubmit)?;
 
+			// Set data to zeros for the whole glyph island
+			// TODO: use `vkCmdClearColorImage` with an image subresource (or xywh region?) to omit unnecessary allocation
+			let zero_bytes_data: Vec<u8> = vec![0x00; size_with_island.area() as usize * 4 /* RGBX */];
+			cmd_buf.update_image(
+				inner.image_view.image(),
+				&zero_bytes_data,
+				[atlas_with_island_min.x as u32, atlas_with_island_min.y as u32, 0],
+				Some([size_with_island.width as u32, size_with_island.height as u32, 1]),
+			)?;
+
+			// Upload glyph itself
 			cmd_buf.update_image(
 				inner.image_view.image(),
 				&image.data,
-				[atlas_min.x as _, atlas_min.y as _, 0],
+				[atlas_glyph_min.x as u32, atlas_glyph_min.y as u32, 0],
 				Some([image.width.into(), image.height.into(), 1]),
 			)?;
 
@@ -374,8 +390,8 @@ fn prepare_glyph(
 
 			(
 				GpuCacheStatus::InAtlas {
-					x: atlas_min.x as u16,
-					y: atlas_min.y as u16,
+					x: atlas_glyph_min.x as u16,
+					y: atlas_glyph_min.y as u16,
 					content_type: image.content_type,
 				},
 				Some(allocation.id),