Paint into a target Surface instead of swapping the frame's out

The painters of a pane's body and tag (renderBody and its selection,
gutter, syntax, ANSI and wrap-marker passes; paintPaneTag; paintHeaders;
renderPane; the image and PDF grid paths) take the Surface they paint as a
parameter. The body layer and the tag layers paint straight into their own
temporary surfaces, and the std.mem.swap of p.surface around those calls is
gone. No behaviour change.

1 files changed, 16 insertions, 22 deletions

diff --git a/src/body_layer.zig b/src/body_layer.zig
index aa52957c..db4d9524 100644
--- a/src/body_layer.zig
+++ b/src/body_layer.zig
@@ -145,7 +145,7 @@ test "compact context borders separate source gaps and preserve multiline header
 
 // ---- drawing a pane body into the surface ----
 
-fn paintTerminalSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.PointerRow, bg: [3]u8, fg: ?[3]u8) void {
+fn paintTerminalSelection(p: *Pardes, s: *Surface, pane: *Pane, r: Rect, rows: []const Pane.PointerRow, bg: [3]u8, fg: ?[3]u8) void {
     const body = bodyText(p, p.scratch.allocator(), pane) catch return;
     const raw = pane.body.mode == .tty;
     const tx = r.x + config.GUTTER;
@@ -178,7 +178,7 @@ fn paintTerminalSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.P
             var col = panes.File.rawDisplayCol(line, lo);
             const end = panes.File.rawDisplayCol(line, hi);
             while (col < end and col < width) : (col += 1) {
-                const cell = p.surface.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
+                const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
                 cell.default = false;
                 cell.style.bg = .{ .rgb = bg };
                 if (fg) |ink| cell.style.fg = .{ .rgb = ink };
@@ -187,8 +187,8 @@ fn paintTerminalSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.P
     }
 }
 
-fn paintSourceSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.PointerRow, bg: [3]u8, fg: ?[3]u8) void {
-    if (pane.isTerminal()) return paintTerminalSelection(p, pane, r, rows, bg, fg);
+fn paintSourceSelection(p: *Pardes, s: *Surface, pane: *Pane, r: Rect, rows: []const Pane.PointerRow, bg: [3]u8, fg: ?[3]u8) void {
+    if (pane.isTerminal()) return paintTerminalSelection(p, s, pane, r, rows, bg, fg);
     const terminal_lines = if (pane.file == null) panes.Terminal.cursorLines(p, pane) catch return else &.{};
     const tx = r.x + config.GUTTER;
     const width = r.w -| config.GUTTER;
@@ -209,7 +209,7 @@ fn paintSourceSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.Poi
             var col = prefix + @as(i32, @intCast(panes.File.rawDisplayCol(line[start..], lo - start)));
             const last = prefix + @as(i32, @intCast(panes.File.rawDisplayCol(line[start..], hi - start)));
             while (col < last and col < width) : (col += 1) {
-                const cell = p.surface.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
+                const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
                 cell.default = false;
                 cell.style.bg = .{ .rgb = bg };
                 if (fg) |ink| cell.style.fg = .{ .rgb = ink };
@@ -220,6 +220,7 @@ fn paintSourceSelection(p: *Pardes, pane: *Pane, r: Rect, rows: []const Pane.Poi
 
 pub fn paintPointerSelection(
     p: *Pardes,
+    s: *Surface,
     pane: *Pane,
     r: Rect,
     tx: u16,
@@ -230,8 +231,7 @@ pub fn paintPointerSelection(
     bg: [3]u8,
     fg: ?[3]u8,
 ) void {
-    if (pane.pointerSelection(sl)) |rows| return paintSourceSelection(p, pane, r, rows, bg, fg);
-    const s = &p.surface;
+    if (pane.pointerSelection(sl)) |rows| return paintSourceSelection(p, s, pane, r, rows, bg, fg);
     const r0 = @min(sl.r0, sl.r1);
     const r1 = @max(sl.r0, sl.r1);
     const c0 = @max(0, @min(sl.c0, sl.c1));
@@ -278,13 +278,8 @@ pub fn renderBodyLayer(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rec
     const temporary_cells = try arena.alloc(Cell, @as(usize, r.w) * (logical_rows + pane.tag_rows));
     @memset(temporary_cells, .{});
     var temporary: Surface = .{ .cols = r.w, .rows = @intCast(logical_rows + pane.tag_rows), .cells = temporary_cells };
-    std.mem.swap(Surface, &p.surface, &temporary);
     const synthetic: Rect = .{ .x = 0, .y = 0, .w = r.w, .h = @intCast(logical_rows + pane.tag_rows) };
-    renderBody(p, arena, pane, synthetic, id, id == p.active, false) catch |err| {
-        std.mem.swap(Surface, &p.surface, &temporary);
-        return err;
-    };
-    std.mem.swap(Surface, &p.surface, &temporary);
+    try renderBody(p, &temporary, arena, pane, synthetic, id, id == p.active, false);
     const first_row: usize = if (p.settings.tag_bottom) 0 else pane.tag_rows;
     for (0..logical_rows) |row| {
         const start = (row + first_row) * r.w + config.GUTTER;
@@ -304,8 +299,7 @@ pub fn renderBodyLayer(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rec
     }
 }
 
-pub fn renderBody(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rect, id: usize, active: bool, scrollbar: bool) !void {
-    const s = &p.surface;
+pub fn renderBody(p: *Pardes, s: *Surface, arena: std.mem.Allocator, pane: *Pane, r: Rect, id: usize, active: bool, scrollbar: bool) !void {
     const th = p.theme();
     const chrome = p.chromeTheme();
     const tx = r.x + config.GUTTER;
@@ -343,12 +337,12 @@ pub fn renderBody(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rect, id
     const tz_color = tracy.zone(@src(), "paneRecolor");
     // File layout is independent of whether its producer requests colors.
     if (pane.file) |*f| {
-        panes.File.drawGutter(p, pane, r, tx, tw, body_h, active);
+        panes.File.drawGutter(p, s, pane, r, tx, tw, body_h, active);
         if (p.settings.colors and pane.colorAlgo() != .none)
-            panes.File.recolorSyntax(p, pane, f, r, tx, tw, body_h);
-        panes.File.drawWrapMarkers(p, pane, r, tx, tw, body_h, pane_bg);
+            panes.File.recolorSyntax(p, s, pane, f, r, tx, tw, body_h);
+        panes.File.drawWrapMarkers(p, s, pane, r, tx, tw, body_h, pane_bg);
     } else if (pane.isTerminal() and p.settings.colors) {
-        panes.Terminal.recolorAnsi(p, pane, r, tx, tw, body_h, body);
+        panes.Terminal.recolorAnsi(p, s, pane, r, tx, tw, body_h, body);
     }
     tz_color.end();
 
@@ -366,9 +360,9 @@ pub fn renderBody(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rect, id
             // macOS composes its glass overlay over exactly these.
             const preview_bg = colors.mix(page_rgb, colors.mix(page_rgb, th.sel_bg));
             if (preview.file_word) |word|
-                panes.File.paintWordSelection(p, pane, r, word.row, word.lo, word.hi, preview_bg)
+                panes.File.paintWordSelection(p, s, pane, r, word.row, word.lo, word.hi, preview_bg)
             else if (preview.sel) |sel|
-                paintPointerSelection(p, pane, r, tx, tw, tag_y, body_y, sel, preview_bg, null);
+                paintPointerSelection(p, s, pane, r, tx, tw, tag_y, body_y, sel, preview_bg, null);
         }
     }
     const modal_hover = if (p.look_hover_preview) |preview|
@@ -381,7 +375,7 @@ pub fn renderBody(p: *Pardes, arena: std.mem.Allocator, pane: *Pane, r: Rect, id
         // A select sweep over the tag is the tag's selection, painted there
         // in the tag's own selection colours.
         if (b == pardes.sel_slot and @min(sl.r0, sl.r1) < pane.tag_rows) continue;
-        paintPointerSelection(p, pane, r, tx, tw, tag_y, body_y, sl, sel_btn[b], th.sel_fg);
+        paintPointerSelection(p, s, pane, r, tx, tw, tag_y, body_y, sl, sel_btn[b], th.sel_fg);
     }
     // modal line selection (helix `x`): whole body rows, normal mode only
     if ((pane.body.mode == .normal or modal_hover) and pane.body.msel.active) {