--- /dev/null
+/* String conversion support for graphics terminals.
+
+Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
+
+/* String conversion support.
+
+ Many input methods require access to text surrounding the cursor.
+ They may then request that the text editor remove or substitute
+ that text for something else, for example when providing the
+ ability to ``undo'' or ``edit'' previously composed text. This is
+ most commonly seen in input methods for CJK laguages for X Windows,
+ and is extensively used throughout Android by input methods for all
+ kinds of scripts. */
+
+#include <config.h>
+
+#include "textconv.h"
+#include "buffer.h"
+#include "syntax.h"
+
+\f
+
+/* The window system's text conversion interface.
+ NULL when the window system has not set up text conversion.
+
+ This interface will later be heavily extended on the
+ feature/android branch to deal with Android's much less
+ straightforward text conversion protocols. */
+
+static struct textconv_interface *text_interface;
+
+\f
+
+/* Copy the portion of the current buffer described by BEG, BEG_BYTE,
+ END, END_BYTE to the buffer BUFFER, which is END_BYTE - BEG_BYTEs
+ long. */
+
+static void
+copy_buffer (ptrdiff_t beg, ptrdiff_t beg_byte,
+ ptrdiff_t end, ptrdiff_t end_byte,
+ char *buffer)
+{
+ ptrdiff_t beg0, end0, beg1, end1, size;
+
+ if (beg_byte < GPT_BYTE && GPT_BYTE < end_byte)
+ {
+ /* Two regions, before and after the gap. */
+ beg0 = beg_byte;
+ end0 = GPT_BYTE;
+ beg1 = GPT_BYTE + GAP_SIZE - BEG_BYTE;
+ end1 = end_byte + GAP_SIZE - BEG_BYTE;
+ }
+ else
+ {
+ /* The only region. */
+ beg0 = beg_byte;
+ end0 = end_byte;
+ beg1 = -1;
+ end1 = -1;
+ }
+
+ size = end0 - beg0;
+ memcpy (buffer, BYTE_POS_ADDR (beg0), size);
+ if (beg1 != -1)
+ memcpy (buffer, BEG_ADDR + beg1, end1 - beg1);
+}
+
+\f
+
+/* Conversion query. */
+
+/* Perform the text conversion operation specified in QUERY and return
+ the results.
+
+ Find the text between QUERY->position from point on F's selected
+ window and QUERY->factor times QUERY->direction from that
+ position. Return it in QUERY->text.
+
+ Then, either delete that text from the buffer if QUERY->operation
+ is TEXTCONV_SUBSTITUTION, or return 0.
+
+ Value is 0 if QUERY->operation was not TEXTCONV_SUBSTITUTION
+ or if deleting the text was successful, and 1 otherwise. */
+
+int
+textconv_query (struct frame *f, struct textconv_callback_struct *query)
+{
+ specpdl_ref count;
+ ptrdiff_t pos, pos_byte, end, end_byte;
+ ptrdiff_t temp, temp1;
+ char *buffer;
+
+ /* Save the excursion, as there will be extensive changes to the
+ selected window. */
+ count = SPECPDL_INDEX ();
+ record_unwind_protect_excursion ();
+
+ /* Inhibit quitting. */
+ specbind (Qinhibit_quit, Qt);
+
+ /* Temporarily switch to F's selected window. */
+ Fselect_window (f->selected_window, Qt);
+
+ /* Now find the appropriate text bounds for QUERY. First, move
+ point QUERY->position steps forward or backwards. */
+
+ pos = PT;
+
+ /* If pos is outside the accessible part of the buffer or if it
+ overflows, move back to point or to the extremes of the
+ accessible region. */
+
+ if (INT_ADD_WRAPV (pos, query->position, &pos))
+ pos = PT;
+
+ if (pos < BEGV)
+ pos = BEGV;
+
+ if (pos > ZV)
+ pos = ZV;
+
+ /* Move to pos. */
+ set_point (pos);
+ pos = PT;
+ pos_byte = PT_BYTE;
+
+ /* Now scan forward or backwards according to what is in QUERY. */
+
+ switch (query->direction)
+ {
+ case TEXTCONV_FORWARD_CHAR:
+ /* Move forward by query->factor characters. */
+ if (INT_ADD_WRAPV (pos, query->factor, &end) || end > ZV)
+ end = ZV;
+
+ end_byte = CHAR_TO_BYTE (end);
+ break;
+
+ case TEXTCONV_BACKWARD_CHAR:
+ /* Move backward by query->factor characters. */
+ if (INT_SUBTRACT_WRAPV (pos, query->factor, &end) || end < BEGV)
+ end = BEGV;
+
+ end_byte = CHAR_TO_BYTE (end);
+ break;
+
+ case TEXTCONV_FORWARD_WORD:
+ /* Move forward by query->factor word. */
+ end = scan_words (pos, (EMACS_INT) query->factor);
+
+ if (!end)
+ {
+ end = ZV;
+ end_byte = ZV_BYTE;
+ }
+ else
+ end_byte = CHAR_TO_BYTE (end);
+
+ break;
+
+ case TEXTCONV_BACKWARD_WORD:
+ /* Move backwards by query->factor word. */
+ end = scan_words (pos, 0 - (EMACS_INT) query->factor);
+
+ if (!end)
+ {
+ end = BEGV;
+ end_byte = BEGV_BYTE;
+ }
+ else
+ end_byte = CHAR_TO_BYTE (end);
+
+ break;
+
+ case TEXTCONV_CARET_UP:
+ /* Move upwards one visual line, keeping the column intact. */
+ Fvertical_motion (Fcons (Fcurrent_column (), make_fixnum (-1)),
+ Qnil, Qnil);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_CARET_DOWN:
+ /* Move downwards one visual line, keeping the column
+ intact. */
+ Fvertical_motion (Fcons (Fcurrent_column (), make_fixnum (1)),
+ Qnil, Qnil);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_NEXT_LINE:
+ /* Move one line forward. */
+ scan_newline (pos, pos_byte, ZV, ZV_BYTE,
+ query->factor, false);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_PREVIOUS_LINE:
+ /* Move one line backwards. */
+ scan_newline (pos, pos_byte, BEGV, BEGV_BYTE,
+ 0 - (EMACS_INT) query->factor, false);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_LINE_START:
+ /* Move to the beginning of the line. */
+ Fbeginning_of_line (Qnil);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_LINE_END:
+ /* Move to the end of the line. */
+ Fend_of_line (Qnil);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ case TEXTCONV_ABSOLUTE_POSITION:
+ /* How to implement this is unclear. */
+ SET_PT (query->factor);
+ end = PT;
+ end_byte = PT_BYTE;
+ break;
+
+ default:
+ unbind_to (count, Qnil);
+ return 1;
+ }
+
+ /* Sort end and pos. */
+
+ if (end < pos)
+ {
+ eassert (end_byte < pos_byte);
+ temp = pos_byte;
+ temp1 = pos;
+ pos_byte = end_byte;
+ pos = end;
+ end = temp1;
+ end_byte = temp;
+ }
+
+ /* Return the string first. */
+ buffer = xmalloc (end_byte - pos_byte);
+ copy_buffer (pos, pos_byte, end, end_byte, buffer);
+ query->text.text = buffer;
+ query->text.length = end - pos;
+ query->text.bytes = end_byte - pos_byte;
+
+ /* Next, perform any operation specified. */
+
+ switch (query->operation)
+ {
+ case TEXTCONV_SUBSTITUTION:
+ if (safe_del_range (pos, end))
+ {
+ /* Undo any changes to the excursion. */
+ unbind_to (count, Qnil);
+ return 1;
+ }
+
+ default:
+ }
+
+ /* Undo any changes to the excursion. */
+ unbind_to (count, Qnil);
+ return 0;
+}
+
+\f
+
+/* Window system interface. These are called from the rest of
+ Emacs. */
+
+/* Notice that F's selected window has been set from redisplay.
+ Reset F's input method state. */
+
+void
+report_selected_window_change (struct frame *f)
+{
+ if (!text_interface)
+ return;
+
+ text_interface->reset (f);
+}
+
+/* Register INTERFACE as the text conversion interface. */
+
+void
+register_texconv_interface (struct textconv_interface *interface)
+{
+ text_interface = interface;
+}
--- /dev/null
+/* String conversion support for graphics terminals.
+
+Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
+
+#ifndef _TEXTCONV_H_
+
+#include "lisp.h"
+#include "frame.h"
+
+/* The function pointers in this structure should be filled out by
+ each GUI backend interested in supporting text conversion.
+
+ Finally, register_texconv_interface must be called at some point
+ during terminal initialization. */
+
+struct textconv_interface
+{
+ /* Notice that the text conversion context has changed (which can
+ happen if the window is deleted or switches buffers, or an
+ unexpected buffer change occurs.) */
+ void (*reset) (struct frame *);
+};
+
+\f
+
+enum textconv_caret_direction
+ {
+ TEXTCONV_FORWARD_CHAR,
+ TEXTCONV_BACKWARD_CHAR,
+ TEXTCONV_FORWARD_WORD,
+ TEXTCONV_BACKWARD_WORD,
+ TEXTCONV_CARET_UP,
+ TEXTCONV_CARET_DOWN,
+ TEXTCONV_NEXT_LINE,
+ TEXTCONV_PREVIOUS_LINE,
+ TEXTCONV_LINE_START,
+ TEXTCONV_LINE_END,
+ TEXTCONV_ABSOLUTE_POSITION,
+ };
+
+enum textconv_operation
+ {
+ TEXTCONV_SUBSTITUTION,
+ TEXTCONV_RETRIEVAL,
+ };
+
+/* Structure describing text in a buffer corresponding to a ``struct
+ textconv_callback_struct''. */
+
+struct textconv_conversion_text
+{
+ /* Length of the text in characters and bytes. */
+ size_t length, bytes;
+
+ /* Pointer to the text data. This must be deallocated by the
+ caller. */
+ char *text;
+};
+
+/* Structure describing a single query submitted by the input
+ method. */
+
+struct textconv_callback_struct
+{
+ /* Character position, relative to the current spot location, from
+ where on text should be returned. */
+ EMACS_INT position;
+
+ /* The type of scanning to perform to determine either the start or
+ the end of the conversion. */
+ enum textconv_caret_direction direction;
+
+ /* The the number of times for which to repeat the scanning in order
+ to determine the starting position of the text to return. */
+ unsigned short factor;
+
+ /* The operation to perform upon the current buffer contents.
+
+ If this is TEXTCONV_SUBSTITUTION, then the text that is returned
+ will be deleted from the buffer itself.
+
+ Otherwise, the text is simply returned without modifying the
+ buffer contents. */
+ enum textconv_operation operation;
+
+ /* Structure that will be filled with a description of the resulting
+ text. */
+ struct textconv_conversion_text text;
+};
+
+extern int textconv_query (struct frame *, struct textconv_callback_struct *);
+extern void register_texconv_interface (struct textconv_interface *);
+
+#endif /* _TEXTCONV_H_ */
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