fix PDF mouse-wheel scrolling jumping multiple pages

1 files changed, 38 insertions, 3 deletions

diff --git a/src/tty/tty.zig b/src/tty/tty.zig
index 6f7cc5ba..343452b5 100644
--- a/src/tty/tty.zig
+++ b/src/tty/tty.zig
@@ -176,6 +176,31 @@ fn kittyImageRepresentable(place: pardes.ImagePlace) bool {
         place.iw <= std.math.maxInt(u16) and place.ih <= std.math.maxInt(u16);
 }
 
+const PdfWheelTarget = struct { pane: usize, page: usize };
+
+/// A native PDF's page geometry is invalid between `setPdfPage` and the next
+/// render. Remember the page under a vertical wheel press so the input batch
+/// can stop exactly when that press crosses a page boundary. The following
+/// queued wheel report then sees the newly rastered page instead of treating
+/// missing geometry as another page-wise fallback.
+fn nativePdfWheelTarget(core: *const pardes.Pardes, mouse: vaxis.Mouse) ?PdfWheelTarget {
+    if (comptime !pardes.pdf_enabled) return null;
+    if (!core.native_images or mouse.type != .press or
+        (mouse.button != .wheel_up and mouse.button != .wheel_down) or
+        mouse.col < 0 or mouse.row < 0) return null;
+    const col: u16 = @intCast(mouse.col);
+    const row: u16 = @intCast(mouse.row);
+    for (core.panes, 0..) |slot, id| {
+        const pane = slot orelse continue;
+        const rect = core.rects[id];
+        if (col < rect.x or col >= rect.x + rect.w or
+            row < rect.y or row >= rect.y + rect.h) continue;
+        const page = pane.pdfPage() orelse return null;
+        return .{ .pane = id, .page = page };
+    }
+    return null;
+}
+
 pub fn run(init: std.process.Init, opts: pardes.Options) !void {
     const io = init.io;
     const gpa = init.gpa;
@@ -353,12 +378,15 @@ pub fn run(init: std.process.Init, opts: pardes.Options) !void {
         const tz_event = tracy.zone(@src(), "event");
         // Apply every queued INPUT event, then render ONCE — the gui shell
         // drains SDL's queue the same way. Without this a wheel flick is fifty
-        // full render+repaint (and re-highlight) cycles instead of one.
-        // pty output keeps a frame per chunk: progress paints as it arrives.
+        // full render+repaint (and re-highlight) cycles instead of one. A
+        // native PDF page crossing is the one input boundary below: its next
+        // wheel report needs geometry produced by this render. Pty output also
+        // keeps a frame per chunk so progress paints as it arrives.
         var stop = false;
         var batch: usize = 0;
         while (true) {
             var output = false;
+            var native_pdf_page_changed = false;
             switch (event) {
                 .nop, .tick => {},
                 .quit => stop = true,
@@ -390,6 +418,7 @@ pub fn run(init: std.process.Init, opts: pardes.Options) !void {
                     .shift = key.mods.shift,
                 } }),
                 .mouse => |m| {
+                    const pdf_before = nativePdfWheelTarget(core, m);
                     const button: ?pardes.Mouse.Button = switch (m.button) {
                         .left => .left,
                         .middle => .middle,
@@ -413,6 +442,12 @@ pub fn run(init: std.process.Init, opts: pardes.Options) !void {
                         .row = @intCast(m.row),
                         .ctrl = m.mods.ctrl,
                     } });
+                    if (pdf_before) |before| {
+                        if (core.panes[before.pane]) |pane| {
+                            if (pane.pdfPage()) |page|
+                                native_pdf_page_changed = page != before.page;
+                        }
+                    }
                 },
                 .paste => |bytes| {
                     core.update(.{ .paste = bytes });
@@ -434,7 +469,7 @@ pub fn run(init: std.process.Init, opts: pardes.Options) !void {
                 },
             }
             batch += 1;
-            if (stop or output or batch >= 64) break;
+            if (stop or output or native_pdf_page_changed or batch >= 64) break;
             event = (try loop.tryEvent()) orelse break;
         }
         tz_event.end();