Firefox fixes, openWindow security fixes, and few improvements

• Update to libdot 1.26. openWindow & new codec helpers.
• Optimize image display with Blobs & ArrayBuffers.
• Workaround touch focus bug on CrOS.
• Initialising iframe contents asynchronously on FF.
• Add support for new Clipboard API for copying text.
• Push selection logic down into copySelectionToClipboard.
• Fix paste event on Firefox.
• terminal: Stop passing down this.document_ when copying.
• Switch to array buffers for sending tty data.
• Provide readable pref strings.
• tests: Switch to a dark theme.
• concat: Stop listing test code in deps.
• Use new lib.f.openWindow helper.

Minor improvements

• Split default/pointer cursor style.
• Avoid using KeyboardEvent.which.
• prefs: Turn default pref settings into proper objects.
• Add paste-on-drop preference.

New context menu

• Update to libdot 1.24. Tool improvements for supporting nightly builds.
• embed: Update examples to use lib.init.
• terminal: Move cursor color to css vars.
• Add support for a context menu.
• keyboard: Add a clearScrollback hook.
• vt: Change CSI-J-3 to clear scrollback.
• terminal: Add HTMLImageElement cast to avoid XSS compilation warnings.
• terminal: Process inverse text attr after bold-as-bright & faint.
• hterm-notify/hterm-show-file: Fix long sequences under screen.
• osc52.sh: Rewrite to match other helper scripts.
• terminal: Workaround FireFox bug with selectAllChildren.

A11y improvements, and keyboard/mouse tweaks

• Update to libdot 1.23. Build improvements, i18n helpers, and npm support.
• mouse: Support horizontal mouse scroll wheel events.
• keyboard: Add more keyboard binding callbacks.
• mouse: Disable default handling for mouse buttons 3 & 4.
• keyboard: Ignore Tab keys in onKeyPress_.
• etc: osc52.el: Fix terminal detection.
• build: mkdist: Delete dead code.
• a11y: Ensure the Page Up button isn't shown when the ScrollPort is focussed.
• build: Convert concat to a python script.
• a11y: Only announce a space character if it is the character actually printed to the screen.
• a11y: Mark offscreen rows that hold selection as hidden.
• a11y: Update the selection when accessibility is enabled even if it's collapsed.
• test: Remove invalid page-down-all-rows-visible test.
• a11y: Add announcements of the Space character.
• a11y: Handle announcements of selection changes.
• a11y: Simplify handling of duplicate live output.
• a11y: Change to have a role="log".
• a11y: Announce messages shown by showOverlay.
• a11y: Fix announcement of current scrolled percentage.
• a11y: Don't announce page up/down at the top/bottom of the screen.
• a11y: Fix an assertion failure in hterm.AccessibilityReader.
• test: Add simple test page.
• test: Add/update various test data files.
• a11y: Make it possible to enable/disable accessibility at runtime.
• a11y: Announce the current screen content on Page up/down.
• a11y: Add skip-links to allow screen readers to scroll the terminal.

Minor tweaks

• prefs: Add COLORTERM to default env.
• vt: Automatically hide the mouse cursor while typing.
• vt: Improve & document mouse cursor customization.

A11y (screen reader) improvements & keyboard/mouse fixes

• Update to libdot 1.22. Unicode 11.0.0 updates and new helpers.
• osc52.vim: Split base64 output when using get_OSC52_DCS for screen.
• keyboard: Add media key handling only for Chrome OS systems.
• keyboard: Cleanly handle Firefox keyboard deviations.
• keyboard: Update Chromebook media bindings.
• build: Fix base64 usage on macOS.
• vt: Strip most control chars out for bracketed paste.
• keyboard: Improve addKeyDef documentation.
• mouse: Don't use user-configured word break matches when ctrl-clicking on urls.
• mouse: Double click should expand selection whether "copy-on-select" is on or off.
• a11y: Hide invisible elements from the screen reader.
• a11y: Add the aria-readonly attribute to the x-screen element.
• vt: Fix initial cursor display to match internal state.
• vtscope: Fix python-3 print func handling.
• prefs: Add Noto Sans Mono to the default font list.
• Clean up code a bit to pass linting.
• a11y: Add basic support for announcing command output to AT in hterm.
• a11y: Improve accessibility command output.
• tests: Add callbacks with image loading.
• terminal: Preserve selection when scrolling collapsed selections.
• Crush all images.
• tests: Fix floating point rounding error in Terminal.dimensions.
• vt: Unbreak legacy mouse wheel encoding.
• vt: Implement OSC 104 (color reset) support.
• vt: DECALN: Fix cursor position.
• prefs: Improve descriptions and translation tips.

Extended underlying support

• Add support for changing underline style/color.
• README: document our mirrors/release sites.
• Fix typo in autocapitalize attribute.
• Send a signal when the frame is made visible.
• Document expected coding style.
• Fix fallback git value.

Various bug fixes

• Fix typo in mouse wheel reporting (for newer tmux).
• Add sanity check on user font size.
• Overhaul SGR 38/48 handling for ISO 8613-6.
• Fix osc52 vim script in tmux.
• Allow F11 when running in a tab for fullscreen.
• Implement OSC 110/111/112.
• Set charset=utf-8 in html files.
• Check document character set at startup.
• Fix typo in blink preference handling (broke in hterm-1.69).

Standards/compatibility fixes & OSC-8 links & OSC-1337 image features

• change default terminal encoding to utf8
• invert drag & drop format preferences
• handle ISO-8613-6 SGR subparameters
• default all character maps to US/ASCII when resetting
• fix reset after custom text attributes
• separate terminal full & soft reset code paths
• move vt reset calls into the terminal layer
• reset SGR attributes during soft resets
• move cursor save/restore state from per-terminal to per-screen
• rename CHA comments to match DEC docs
• support DECSET 1007 for controlling alternate scroll mode
• hoist openUrl to main namespace
• support OSC 8 for hyperlinking text
• add localization logic
• drop max-string-sequence support
• add a test to keep nassh translations in sync
• allow keybindings for unknown keys
• add a default PASS mapping for the Clear key
• use new lib.f.getOs helper
• include all profiles all the time when backing up
• implement OSC 1337 file display/transfer

Many color/style/mouse fixes & features

• Fix parsing multiple SGR true color sequences.
• Add support for double underlining (SGR 21).
• Document a few more CSI options.
• Fix handling of inverse text with true colors.
• Simplify invisible text processing.
• Fix DECSET/DECRST 1048 handling.
• Stop changing color palettes when restoring cursor state.
• Handle X10 & X11 mouse reporting modes.
• Support UTF-8 & SGR mouse reporting modes.
• Optimize mouse move reporting.
• Return early on mouse move events when possible.