Jean-Pierre MartineauandClaude Opus 5.5
3e251a9707
The same rewrite as for the core package. The physical screen of a handheld is now the display, and the computer is the handheld. The comment on FONT_ENV now says that it is the environment variable. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
38 lines
2.3 KiB
Python
38 lines
2.3 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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"""The emulator: MeshTerm draws a handheld's display itself, on the handheld or in a window.
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**Not a strict emulator.** Nothing here runs the processor or the operating system of the
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handheld. MeshTerm runs as itself, on the machine that runs this package. The emulator
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copies the display and the keyboard of the handheld: the size of the display in pixels,
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the character grid on the display, the font that draws each glyph, the colours that the
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display can show and how bold changes them, and the keyboard keys that drive the F-key
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lane. Thus the screen in the window obeys the same constraints as the screen of the
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handheld. The emulator copies the display. It does not emulate the machine.
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The emulator started as the *console host* of the Cardputer Zero: the program that a text
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app runs in. On that handheld, it is still exactly that. The Cardputer Zero has no text
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console that an app can use. Its launcher owns the screen, the framebuffer console of the
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kernel is off, and a store app cannot run as root to turn it on again. An app gets only
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the framebuffer itself and the event device file of the keyboard. Thus MeshTerm brings its
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own terminal. This package runs the ordinary TUI in the same process:
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* prompt_toolkit writes to an output of a fixed size. The bytes of that output go to a
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small VT parser (:mod:`.vt`) instead of to a terminal.
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* prompt_toolkit reads from a pipe, and this package types key presses into that pipe
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(:mod:`.keys`).
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A 6×12 bitmap font draws the parsed cell grid into pixels (:mod:`.font`, :mod:`.raster`).
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The pixels go to one of two front ends:
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* On the Cardputer Zero: the framebuffer that the launcher gives, with key presses from
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the event device file of the keyboard (:mod:`.framebuffer`).
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* On a desktop: a window that draws the display of the handheld at a larger scale, with
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key presses from the desktop keyboard (:mod:`.window`). The code path is the same as on
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the handheld, except at these two ends.
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Nothing in the TUI knows that it is emulated. When the terminal wrappers of the session
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are off, the session takes its input and output from the app session of prompt_toolkit.
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The wrappers are off on these platforms. Thus this package must only set up that session
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and call the CLI as a shell does (:mod:`.run`).
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"""
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