feat: implement stencils

build.zig.zon

@@ -9,8 +9,8 @@
 
     .dependencies = .{
         .zenolith = .{
-            .url = "git+https://git.mzte.de/zenolith/zenolith.git#6f318242d7bb5dad079e5ad6421900744e5d03b4",
-            .hash = "122034a7efb688149b6251c939407e31b1574de418c947a9b25478957d91aad69f5f",
+            .url = "git+https://git.mzte.de/zenolith/zenolith.git#431cd4adf7f141a83887a7c09375628d79d1962a",
+            .hash = "12206042c1f7851e8b1626d5b57b6054ac9f01a0476525823d34ab62f543e31aec23",
         },
 
         .sdl2 = .{

src/Sdl2Painter.zig

@@ -13,9 +13,15 @@ const Sdl2Painter = @This();
 
 pub fn rect(
     self: *Sdl2Painter,
+    selfp: *zenolith.painter.Painter,
     rectangle: zenolith.layout.Rectangle,
     color: zenolith.Color,
 ) !void {
+    const clip_rect = if (selfp.data.peekStencil()) |stenc|
+        rectangle.intersection(stenc) orelse return
+    else
+        rectangle;
+
     if (c.SDL_SetRenderDrawColor(
         self.renderer,
         color.r,
@@ -24,25 +30,54 @@ pub fn rect(
         color.a,
     ) != 0) return error.Render;
 
-    if (c.SDL_RenderFillRect(self.renderer, &util.toSdlRect(rectangle)) != 0) return error.Render;
+    if (c.SDL_RenderFillRect(self.renderer, &util.toSdlRect(clip_rect)) != 0) return error.Render;
 }
 
 pub fn texturedRect(
     self: *Sdl2Painter,
+    selfp: *zenolith.painter.Painter,
     src: zenolith.layout.Rectangle,
     dest: zenolith.layout.Rectangle,
     texture: *zenolith.texture.Texture,
 ) !void {
+    const clip_dest = if (selfp.data.peekStencil()) |stenc|
+        dest.intersection(stenc) orelse return
+    else
+        dest;
+
+    // TODO: this is simply inacceptable... but it works
+    const x_scale: f64 = @as(f64, @floatFromInt(clip_dest.size.width)) /
+        @as(f64, @floatFromInt(dest.size.width));
+    const y_scale: f64 = @as(f64, @floatFromInt(clip_dest.size.height)) /
+        @as(f64, @floatFromInt(dest.size.height));
+
+    const x_mv_scale: f64 = @as(f64, @floatFromInt(clip_dest.pos.x - dest.pos.x)) /
+        @as(f64, @floatFromInt(dest.size.width));
+    const y_mv_scale: f64 = @as(f64, @floatFromInt(clip_dest.pos.y - dest.pos.y)) /
+        @as(f64, @floatFromInt(dest.size.height));
+
+    const clip_src = zenolith.layout.Rectangle{
+        .pos = .{
+            .x = src.pos.x + @as(i32, @intFromFloat(@as(f64, @floatFromInt(src.size.width)) * x_mv_scale)),
+            .y = src.pos.y + @as(i32, @intFromFloat(@as(f64, @floatFromInt(src.size.height)) * y_mv_scale)),
+        },
+        .size = .{
+            .width = @intFromFloat(@as(f64, @floatFromInt(src.size.width)) * x_scale),
+            .height = @intFromFloat(@as(f64, @floatFromInt(src.size.height)) * y_scale),
+        },
+    };
+
     if (c.SDL_RenderCopy(
         self.renderer,
         (texture.downcast(Sdl2Texture) orelse unreachable).tex,
-        &util.toSdlRect(src),
-        &util.toSdlRect(dest),
+        &util.toSdlRect(clip_src),
+        &util.toSdlRect(clip_dest),
     ) != 0) return error.Render;
 }
 
 pub fn span(
     self: *Sdl2Painter,
+    selfp: *zenolith.painter.Painter,
     pos: zenolith.layout.Position,
     zspan: zenolith.text.Span,
 ) !void {
@@ -57,18 +92,32 @@ pub fn span(
     if (c.SDL_SetTextureAlphaMod(font.atlas, zspan.style.color.a) != 0) return error.Render;
 
     for (zspan.glyphs.items) |g| {
+        // This is sound as the span will have already gotten the glyph from the font,
+        // causing it to add it to the map.
+        const sprite_rect = font.getSprite(g.glyph.codepoint, zspan.style.size) orelse unreachable;
+
+        const rectangle = zenolith.layout.Rectangle{
+            .pos = pos.add(g.position),
+            .size = g.glyph.size,
+        };
+
+        const clip_rect = if (selfp.data.peekStencil()) |stenc|
+            rectangle.intersection(stenc) orelse continue
+        else
+            rectangle;
+
+        std.debug.assert(std.meta.eql(sprite_rect.size, rectangle.size));
+
+        const sprite_clip = zenolith.layout.Rectangle{
+            .pos = sprite_rect.pos.add(clip_rect.pos.sub(rectangle.pos)),
+            .size = clip_rect.size,
+        };
+
         if (c.SDL_RenderCopy(
             self.renderer,
             font.atlas,
-            &util.toSdlRect(
-                // This is sound as the span will have already gotten the glyph from the font,
-                // causing it to add it to the map.
-                font.getSprite(g.glyph.codepoint, zspan.style.size) orelse unreachable,
-            ),
-            &util.toSdlRect(.{
-                .pos = pos.add(g.position),
-                .size = g.glyph.size,
-            }),
+            &util.toSdlRect(sprite_clip),
+            &util.toSdlRect(clip_rect),
         ) != 0) return error.Render;
     }
 }

src/Sdl2Platform.zig

@@ -290,7 +290,11 @@ pub fn run(
         if (c.SDL_SetRenderDrawColor(self.renderer, 0, 0, 0, 0xff) != 0) return error.Render;
         if (c.SDL_RenderClear(self.renderer) != 0) return error.Render;
 
-        var painter = zenolith.painter.Painter.create(Sdl2Painter{ .renderer = self.renderer }, {});
+        var painter = zenolith.painter.Painter.create(
+            Sdl2Painter{ .renderer = self.renderer },
+            zenolith.painter.PainterData.init(root.data.allocator),
+        );
+        defer painter.data.deinit();
         const current_time = std.time.nanoTimestamp();
         try zenolith.treevent.fire(root, zenolith.treevent.Draw{
             .painter = &painter,