FIX: CPU and latency (#9-#16), #17 backlog, v0.1.4

.github/release-notes.md

@@ -1,19 +1,47 @@
-rexplorer's context menu on the desktop: right-click the desktop and get the same menu as in a rexplorer folder.
+Lower CPU use and quicker responses: rexplorer no longer reloads a folder on every change notification, preloads
+less, and keeps slow shell work off the window's thread.
 
 **Install.** Download the zip, extract it, and run `rexplorer.exe` to try it. `rexplorer.exe --install` makes it
 the default file manager for your user; it needs no administrator rights. Already installed? Run the new
 `rexplorer.exe --install` to replace the old copy. Undo with
 `%LOCALAPPDATA%\Programs\rexplorer\rexplorer.exe --uninstall`.
 
-**Changes.**
-- Desktop context menu: a small helper (`rexplorer --desktop`, one per sign-in) shows rexplorer's menu when you
-  right-click the desktop. On icons it has the shell's verbs for the selection; on the background it has View,
-  Sort by, Refresh and Paste plus the shell's background verbs. Explorer still draws the desktop, the taskbar and
-  Start. Install adds a Startup shortcut so the helper runs at every sign-in, and starts it right away.
-- Install and uninstall close a running helper before they replace or remove the exe, and start it again
-  afterwards. If an install fails, Roll back also removes or restores the Start menu and Startup shortcuts.
-- Not covered yet: right-dragging desktop icons (the press goes to the menu), and Shift+F10 or the Menu key on the
-  desktop, which still open Explorer's menu.
+**CPU and latency.** Measured on the developer's machine against 0.1.1.
+- Change notifications (#11): a folder whose files keep changing reloads at most once a second, and not at all while
+  the window is minimized; restoring it catches up once. A folder under constant writes costs about a third of the
+  CPU it did, and about none while minimized. Idle CPU is about 7x lower.
+- Sidebar (#12): it is rebuilt every 30 seconds while shown instead of every 5, and right away when a drive is added
+  or removed.
+- Hover preview (#9): only text files and light images (png, jpg, gif, bmp, webp, ico) are loaded ahead when the
+  pointer rests on them, only once it has stopped moving for the hover delay, and only while rexplorer is the
+  active window. PDFs and other heavy types are previewed only when selected.
+- Preview pane (#10): showing the same file again keeps its preview handler instead of starting a new one.
+- Home (#13): it is built faster at startup, and its icons repaint in batches.
+- First launch (#14): Windows' system icons are exported only when the theme uses them (`icon_theme=default`).
+  First-launch CPU went from about 4.5 s to 0.5 s.
+- Icons view (#15): heavy types (PDF, video, documents) show icons instead of rendered thumbnails; pictures keep
+  thumbnails, and only pictures are loaded ahead of the scroll.
+- Open terminal (#16): it starts in the background, so the window no longer waits for it.
+- From the #17 backlog:
+  - Sorting runs on the load thread. Cell text and icons are cached, so repaints and type-to-select no longer ask
+    the shell again.
+  - Switching tabs reloads a folder only if it changed while the tab was in the background.
+  - Thumbnails of rows scrolled past are skipped, and thumbnails are scaled off the window's thread.
+  - Copy, Cut, Paste, Delete and Properties no longer load every shell extension (Copy: about 350 ms down to 80 ms).
+  - A navigation that is superseded stops early. Search stops at its result cap, and the elevated index search can
+    be cancelled.
+  - The breadcrumb chevron no longer lists network folders, the hidden folder tree is not kept in sync, and the
+    text preview reads up to 64 KB.
+  - A second launch waits for a busy first window instead of opening its own window after 3 s.
+
+**Fixes.**
+- Sorting keeps the selection on the same files. Before, it stayed on the same row positions, so a Delete right
+  after a sort could act on a file you had not picked.
+- Sorting in the Icons and Thumbnails views no longer leaves thumbnails on the wrong files.
+- Open terminal finds Windows Terminal installed outside the Store (scoop, the zip) on PATH, and never runs a
+  `wt.exe` found through the browsed folder.
+
+**Roadmap.** `VERSION-1-X.md` lists what a stable 1.0 needs; each item has an issue in the v1.0 milestone (#71).
 
 The binary is built by GitHub Actions from the tagged commit; `SHA256SUMS.txt` lists the checksums. It is not
 code-signed, so SmartScreen may warn on first run.

README.md

@@ -74,7 +74,7 @@ Sidebar, every row read from the shell with its localized name and icon:
 Click a row to go there; the row of the current folder, or of its nearest ancestor, is highlighted. Right-click a
 pinned Quick Access folder for **Unpin from Home**, a frequent (not pinned) one for **Pin to Home**, a bookmark for
 **Remove bookmark** (its `bookmark.<label>` line leaves settings.ini). Pinned and frequent are told apart by the
-shell's `System.Home.IsPinned` property. The rows are built on a worker thread, rebuilt every 5 s while the window is active and right after
+shell's `System.Home.IsPinned` property. The rows are built on a worker thread, rebuilt when the window is activated, every 30 s while the sidebar shows, when a drive comes or goes, and right after
 a pin or unpin from rexplorer, so the sidebar fills in after the first listing. More > **Folder tree** shows the
 shell's folder tree in the sidebar's place (choose it again for the sidebar).
 
@@ -406,9 +406,10 @@ Icon themes: `icons\<name>\` holds PNGs named by extension (`rs.png`, `pdf.png`.
 the system icons, for folders, archive members and search results alike. A folder whose name ends in a themed
 extension (a zip, a folder to the shell) gets that extension's PNG. PNGs are decoded on first use, so a theme of
 hundreds costs nothing at startup. `icons\default` is written on first run: `folder.png` and `file.png` in the
-theme's accent, then, in the background (about ten seconds), Windows' own 48 px icon for every extension registered
-on the machine that has an icon of its own (about 560 here; `system-icons.txt` lists them and marks the export
-done; delete it to pick up extensions registered since). The export never overwrites a PNG, so edit or replace any.
+theme's accent. Only while a theme sets `icon_theme=default`, the app also exports, in the background (about ten
+seconds), Windows' own 48 px icon for every extension registered on the machine that has an icon of its own (about
+560 here; `system-icons.txt` lists them and marks the export done; delete it to pick up extensions registered
+since). The export never overwrites a PNG, so edit or replace any.
 
 Opening-app icons: a file type Windows registers without an icon of its own shows Explorer's blank page (`.ps1` on
 a machine whose PowerShell file type was never registered, `.py` or `.md` opened with an editor that registers no