; * etc/PROBLEMS: Remove several resolved problems.
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Po Lu
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1 changed files with 26 additions and 98 deletions
124
etc/PROBLEMS
124
etc/PROBLEMS
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@ -3406,26 +3406,21 @@ this and many other problems do not exist on the regular X builds.
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** Text displayed in the default monospace font looks horrible.
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Droid Sans Mono (the default Monospace font which comes with Android)
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incorporates instruction code designed for Microsoft's proprietary
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TrueType font scaler. When this code is executed by Emacs to instruct
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a glyph containing more than one component, it tries to address
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"reference points" which are set to the values of two extra "phantom
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points" in the glyph, that are a proprietary extension of the MS font
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scaler.
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TrueType fonts incorporate instruction code executed by the font
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scaler (the component responsible for transforming outlines into
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bitmap images capable of being displayed onscreen), in order that
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features of each glyph might be aligned to pixel boundaries
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intelligently, preventing faintness while maintaining the shape of its
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features. The substandard instruction code provided by the monospace
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font distributed with Android misplaces features of such glyphs as "E"
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and "F" between point sizes of 16 and 24, resulting in noticeable
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whitespace inconsistencies with other glyphs. Furthermore, the
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vertical stem in the glyph "T" is positioned too far to the left.
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Emacs does not support these extensions, and as a result characters
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such as
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ĥ
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display incorrectly, with the right most edge of the `h' component
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stretched very far out to the right, on some low density displays.
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The solution is to replace the MS-specific hinting code in Droid Sans
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Mono with automatically generated code from the FreeType project's
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"ttfautohint" program. First, extract
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'/system/fonts/DroidSansMono.ttf' from your device:
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The remedy for this is to replace the instruction code with
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automatically generated code from the FreeType project's "ttfautohint"
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program. First, extract '/system/fonts/DroidSansMono.ttf' from your
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device:
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$ adb pull /system/fonts/DroidSansMono.ttf
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/system/fonts/DroidSansMono.ttf: 1 file pulled, 0 skipped.
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@ -3448,85 +3443,18 @@ allowed by free versions of Android, such as Replicant):
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or to the user fonts directory described in the "Android Fonts" node
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of the Emacs manual. You may want to perform this procedure even if
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you are not seeing problems with character display, as the
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automatically generated instructions result in superior display
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results that are easier to read.
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We have been told that the default Sans font under Android 2.3.7,
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named "Droid Sans", also exhibits this problem. The procedure for
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repairing the font is identical to the procedure outlined above,
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albeit with "DroidSansMono" replaced by simply "DroidSans".
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** The "Anonymous Pro" font displays incorrectly.
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Glyph instruction code within the Anonymous Pro font relies on
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undocumented features of the Microsoft TrueType font scaler, namely
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that the scaler always resets the "projection" and "freedom" vector
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interpreter control registers after the execution of the font
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pre-program, which sets them to a value that is perpendicular to the
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horizontal plane of movement.
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Since Emacs does not provide this "feature", various points inside
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glyphs are moved vertically rather than horizontally when a glyph
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program later executes an instruction such as "MIRP" (Move Indirect
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Relative Point) that moves and measures points along the axis
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specified by those registers.
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This can be remedied in two ways; the first (and the easiest) is to
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replace its instruction code with that supplied by "ttfautohint", as
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depicted above. The second is to patch the instruction code inside
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the font itself, using the "ttx" utility:
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https://fonttools.readthedocs.io/en/latest/ttx.html
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First, convert the font to its XML representation:
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$ ttx Anonymous_Pro.ttf
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then, find the end of the section labeled 'prep':
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<prep>
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<assembly>
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[...]
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ROUND[01] /* Round */
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RTG[ ] /* RoundToGrid */
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WCVTP[ ] /* WriteCVTInPixels */
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</assembly>
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</prep>
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and insert the following instruction immediately before the closing
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'/assembly' tag, so as to reset the interpreter control registers back
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to their default values prior to the completion of the pre-program:
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SVTCA[1] /* Set Vector registers to Control Axis X */
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Then, reassemble the font from the modified XML:
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$ ttx Anonymous_Pro.ttx
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which should produce a modified font by the name of
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Anonymous_Pro#1.ttf.
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** The "IBM Plex Mono" font displays incorrectly.
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This problem is precipitated by an attempt to exploit the undocumented
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feature of the MS font scaler explicated within the previous heading.
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Its remedy is also unsurprisingly alike the fix described there: both
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patching the preprogram to reset the point movement vectors and
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replacing the instruction code with code generated by "ttfautohint"
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will adequately resolve the problem.
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you are not experiencing problems with character display, as the
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automatically generated instructions result in more legible text.
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** Glyphs are missing within the "Arial" font or it does not load.
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On account of its origins at Microsoft, instruction code included
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within this font is awash with references to behavior specific to the
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MS scaler. It is incorrigibly broken, to a degree that even
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"ttfautohint" cannot repair; your only recourse is to select some
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other font.
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This issue may extend beyond Arial to encompass a larger selection of
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fonts designed by Microsoft.
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Old versions of this font included instruction code that assumed a
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degree of latitude from the Microsoft font scaler, which grants fonts
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leave to address nonexistent points without aborting the scaling
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process, among other invalid TrueType operations. This issue may
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extend beyond Arial to encompass a larger selection of old fonts
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designed by Microsoft or Monotype; most of the time, installing newer
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versions of such fonts will suffice.
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** Some TrueType test fonts don't work.
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@ -3554,9 +3482,9 @@ Executing instruction code is not a strict requirement for producing
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correct display results from most current fonts. If a font's
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instruction code produces results that are merely unpleasing, but not
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incorrect, then the font was presumably not designed for Emacs's
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scaler. If its uninstructed glyphs are satisfactory (such as if your
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screen resolution is high to the extent that scaling artifacts prove
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invisible), disable instruction code execution by appending its family
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scaler. If its uninstructed glyphs are satisfactory (such as when
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your screen resolution is high enough to ameliorate scaling
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artifacts), disable instruction code execution by appending its family
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name to the variable 'sfnt-uninstructable-font-regexp', then
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restarting Emacs.
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