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[PR #15783] Rewrite COOKED_READ_DATA #30737

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opened 2026-01-31 09:42:40 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:42:40 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/15783

State: closed
Merged: Yes

This massive refactoring has two goals:

  • Enable us to go beyond UCS-2 support for input editing
  • Bring clarity into COOKED_READ_DATA's inner workings

Unfortunately, over time, knowledge about its exact operation was lost.
While the new code is still complex it reduces the amount of code by 4x
which will make preserving knowledge hopefully significantly easier.

The new implementation is simpler and slower than the old one in a way,
because every time the input line is modified it's rewritten to the text
buffer from scratch. This however massively simplifies the underlying
algorithm and the amount of state that needs to be tracked and results
in a significant reduction in code size. It also makes it more robust,
because there's less code now that can be incorrect.

This "optimization laziness" can be afforded due the recent >10x
improvements to TextBuffer's text ingestion performance.
For short inputs (<1000 characters) I still expect this implementation
to outperform the conhost from the past.
It has received one optimization already however: While reading text
from the InputBuffer we'll now defer writing into the TextBuffer
until we've stopped reading. This improves the overhead of pasting text
from O(n^2) to O(n), which is immediately noticeable for inputs >100kB.

Resizing the text buffer still ends up corrupting the input line
however, which unfortunately cannot be fixed in COOKED_READ_DATA.
The issue occurs due to bugs in TextBuffer::Reflow itself, as it
misplaces the cursor if the prompt is on the last line of the buffer.

Closes #1377
Closes #1503
Closes #4628
Closes #4975
Closes #5033
Closes #8008

This commit is required to fix #797

Validation Steps Performed

  • ASCII input ✅
  • Chinese input (中文維基百科) ❔
    • Resizing the window properly wraps/unwraps wide glyphs ❌
      Broken due to TextBuffer::Reflow bugs
  • Surrogate pair input (🙂) ❔
    • Resizing the window properly wraps/unwraps surrogate pairs ❌
      Broken due to TextBuffer::Reflow bugs
  • In cmd.exe
    • Create 2 file: "a😊b.txt" and "a😟b.txt"
    • Press tab: Autocompletes "a😊b.txt" ✅
    • Navigate the cursor right past the "a"
    • Press tab twice: Autocompletes "a😟b.txt" ✅
  • Backspace deletes preceding glyphs ✅
  • Ctrl+Backspace deletes preceding words ✅
  • Escape clears input ✅
  • Home navigates to start ✅
  • Ctrl+Home deletes text between cursor and start ✅
  • End navigates to end ✅
  • Ctrl+End deletes text between cursor and end ✅
  • Left navigates over previous code points ✅
  • Ctrl+Left navigates to previous word-starts ✅
  • Right and F1 navigate over next code points ✅
    • Pressing right at the end of input copies characters
      from the previous command ✅
  • Ctrl+Right navigates to next word-ends ✅
  • Insert toggles overwrite mode ✅
  • Delete deletes next code point ✅
  • Up and F5 cycle through history ✅
    • Doesn't crash with no history ✅
    • Stops at first entry ✅
  • Down cycles through history ✅
    • Doesn't crash with no history ✅
    • Stops at last entry ✅
  • PageUp retrieves the oldest command ✅
  • PageDown retrieves the newest command ✅
  • F2 starts "copy to char" prompt ✅
    • Escape dismisses prompt ✅
    • Typing a character copies text from the previous command up
      until that character into the current buffer (acts identical
      to F3, but with automatic character search) ✅
  • F3 copies the previous command into the current buffer,
    starting at the current cursor position,
    for as many characters as possible ✅
    • Doesn't erase trailing text if the current buffer
      is longer than the previous command ✅
    • Puts the cursor at the end of the copied text ✅
  • F4 starts "copy from char" prompt ✅
    • Escape dismisses prompt ✅
    • Erases text between the current cursor position and the
      first instance of a given char (but not including it) ✅
  • F6 inserts Ctrl+Z ✅
  • F7 without modifiers starts "command list" prompt ✅
    • Escape dismisses prompt ✅
    • Minimum size of 40x10 characters ✅
    • Width expands to fit the widest history command ✅
    • Height expands up to 20 rows with longer histories ✅
    • F9 starts "command number" prompt ✅
    • Left/Right paste replace the buffer with the given command ✅
      • And put cursor at the end of the buffer ✅
    • Up/Down navigate selection through history ✅
      • Stops at start/end with <10 entries ✅
      • Stops at start/end with >20 entries ✅
      • Wide text rendering during pagination with >20 entries ✅
    • Shift+Up/Down moves history items around ✅
    • Home navigates to first entry ✅
    • End navigates to last entry ✅
    • PageUp navigates by 20 items at a time or to first ✅
    • PageDown navigates by 20 items at a time or to last ✅
  • Alt+F7 clears command history ✅
  • F8 cycles through commands that start with the same text as
    the current buffer up until the current cursor position ✅
    • Doesn't crash with no history ✅
  • F9 starts "command number" prompt ✅
    • Escape dismisses prompt ✅
    • Ignores non-ASCII-decimal characters ✅
    • Allows entering between 1 and 5 digits ✅
    • Pressing Enter fetches the given command from the history ✅
  • Alt+F10 clears doskey aliases ✅
**Original Pull Request:** https://github.com/microsoft/terminal/pull/15783 **State:** closed **Merged:** Yes --- This massive refactoring has two goals: * Enable us to go beyond UCS-2 support for input editing * Bring clarity into `COOKED_READ_DATA`'s inner workings Unfortunately, over time, knowledge about its exact operation was lost. While the new code is still complex it reduces the amount of code by 4x which will make preserving knowledge hopefully significantly easier. The new implementation is simpler and slower than the old one in a way, because every time the input line is modified it's rewritten to the text buffer from scratch. This however massively simplifies the underlying algorithm and the amount of state that needs to be tracked and results in a significant reduction in code size. It also makes it more robust, because there's less code now that can be incorrect. This "optimization laziness" can be afforded due the recent >10x improvements to `TextBuffer`'s text ingestion performance. For short inputs (<1000 characters) I still expect this implementation to outperform the conhost from the past. It has received one optimization already however: While reading text from the `InputBuffer` we'll now defer writing into the `TextBuffer` until we've stopped reading. This improves the overhead of pasting text from O(n^2) to O(n), which is immediately noticeable for inputs >100kB. Resizing the text buffer still ends up corrupting the input line however, which unfortunately cannot be fixed in `COOKED_READ_DATA`. The issue occurs due to bugs in `TextBuffer::Reflow` itself, as it misplaces the cursor if the prompt is on the last line of the buffer. Closes #1377 Closes #1503 Closes #4628 Closes #4975 Closes #5033 Closes #8008 This commit is required to fix #797 ## Validation Steps Performed * ASCII input ✅ * Chinese input (中文維基百科) ❔ * Resizing the window properly wraps/unwraps wide glyphs ❌ Broken due to `TextBuffer::Reflow` bugs * Surrogate pair input (🙂) ❔ * Resizing the window properly wraps/unwraps surrogate pairs ❌ Broken due to `TextBuffer::Reflow` bugs * In cmd.exe * Create 2 file: "a😊b.txt" and "a😟b.txt" * Press tab: Autocompletes "a😊b.txt" ✅ * Navigate the cursor right past the "a" * Press tab twice: Autocompletes "a😟b.txt" ✅ * Backspace deletes preceding glyphs ✅ * Ctrl+Backspace deletes preceding words ✅ * Escape clears input ✅ * Home navigates to start ✅ * Ctrl+Home deletes text between cursor and start ✅ * End navigates to end ✅ * Ctrl+End deletes text between cursor and end ✅ * Left navigates over previous code points ✅ * Ctrl+Left navigates to previous word-starts ✅ * Right and F1 navigate over next code points ✅ * Pressing right at the end of input copies characters from the previous command ✅ * Ctrl+Right navigates to next word-ends ✅ * Insert toggles overwrite mode ✅ * Delete deletes next code point ✅ * Up and F5 cycle through history ✅ * Doesn't crash with no history ✅ * Stops at first entry ✅ * Down cycles through history ✅ * Doesn't crash with no history ✅ * Stops at last entry ✅ * PageUp retrieves the oldest command ✅ * PageDown retrieves the newest command ✅ * F2 starts "copy to char" prompt ✅ * Escape dismisses prompt ✅ * Typing a character copies text from the previous command up until that character into the current buffer (acts identical to F3, but with automatic character search) ✅ * F3 copies the previous command into the current buffer, starting at the current cursor position, for as many characters as possible ✅ * Doesn't erase trailing text if the current buffer is longer than the previous command ✅ * Puts the cursor at the end of the copied text ✅ * F4 starts "copy from char" prompt ✅ * Escape dismisses prompt ✅ * Erases text between the current cursor position and the first instance of a given char (but not including it) ✅ * F6 inserts Ctrl+Z ✅ * F7 without modifiers starts "command list" prompt ✅ * Escape dismisses prompt ✅ * Minimum size of 40x10 characters ✅ * Width expands to fit the widest history command ✅ * Height expands up to 20 rows with longer histories ✅ * F9 starts "command number" prompt ✅ * Left/Right paste replace the buffer with the given command ✅ * And put cursor at the end of the buffer ✅ * Up/Down navigate selection through history ✅ * Stops at start/end with <10 entries ✅ * Stops at start/end with >20 entries ✅ * Wide text rendering during pagination with >20 entries ✅ * Shift+Up/Down moves history items around ✅ * Home navigates to first entry ✅ * End navigates to last entry ✅ * PageUp navigates by 20 items at a time or to first ✅ * PageDown navigates by 20 items at a time or to last ✅ * Alt+F7 clears command history ✅ * F8 cycles through commands that start with the same text as the current buffer up until the current cursor position ✅ * Doesn't crash with no history ✅ * F9 starts "command number" prompt ✅ * Escape dismisses prompt ✅ * Ignores non-ASCII-decimal characters ✅ * Allows entering between 1 and 5 digits ✅ * Pressing Enter fetches the given command from the history ✅ * Alt+F10 clears doskey aliases ✅
claunia added the pull-request label 2026-01-31 09:42:40 +00:00
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Reference: starred/terminal#30737
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