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| author | Po Lu <luangruo@yahoo.com> | 2022-04-06 12:42:45 +0800 |
|---|---|---|
| committer | Po Lu <luangruo@yahoo.com> | 2022-04-06 12:42:45 +0800 |
| commit | a6f7d0f4e38555080bbdb45dbb414e15d206f548 (patch) | |
| tree | c4dbcd10ca404c2728de27ab2ea6eaf96af79b65 | |
| parent | 62eb57f43871dacb6c7ac1f6e2cdaf7add1414e2 (diff) | |
| download | emacs-a6f7d0f4e38555080bbdb45dbb414e15d206f548.tar.gz emacs-a6f7d0f4e38555080bbdb45dbb414e15d206f548.tar.bz2 emacs-a6f7d0f4e38555080bbdb45dbb414e15d206f548.zip | |
; * src/xterm.c: Improve commentary.
| -rw-r--r-- | src/xterm.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/src/xterm.c b/src/xterm.c index 102447ad7e3..7eef2b488be 100644 --- a/src/xterm.c +++ b/src/xterm.c @@ -142,14 +142,22 @@ along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */ draw text in inverse video, and the cursor graphics context is used to display the cursor in the most common case. + N.B. that some of the other window systems supported by use an + emulation of graphics contexts to hold the foreground and + background colors used in a glyph string, while the some others + ports compute those colors directly based on the colors of the + string's face and its highlight, but only on X are graphics + contexts a data structure inherent to the window system. + COLOR ALLOCATION - In X, pixel values for colors are not guaranteed to correspond to - their individual components. The rules for converting colors into - pixel values are defined by the visual class of each display opened - by Emacs. When a display is opened, a suitable visual is obtained - from the X server, and a colormap is created based on that visual, - which is then used for each frame created. + In (and only in) X, pixel values for colors are not guaranteed to + correspond to their individual components. The rules for + converting colors into pixel values are defined by the visual class + of each display opened by Emacs. When a display is opened, a + suitable visual is obtained from the X server, and a colormap is + created based on that visual, which is then used for each frame + created. The colormap is then used by the X server to convert pixel values from a frame created by Emacs into actual colors which are output @@ -202,6 +210,10 @@ along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */ which is used to determine the color values for given pixel values. + In other window systems supported by Emacs, color allocation is + handled by the window system itself, to whom Emacs simply passes 24 + (or 32-bit) RGB values. + OPTIONAL FEATURES While X servers and client libraries tend to come with many |