view.c: add word wrapping

this is contolled by the wrapcolumn/wc and breakat/brk options

related #142: Word wrap and line breaks
related #932: Vis for Prose?
related #1092: Disabling line wrapping

1 files changed, 86 insertions, 30 deletions

diff --git a/view.c b/view.c
index e5c110d..0b7ce36 100644
--- a/view.c
+++ b/view.c
@@ -80,6 +80,10 @@ struct View {
 	bool need_update;   /* whether view has been redrawn */
 	bool large_file;    /* optimize for displaying large files */
 	int colorcolumn;
+	char *breakat;  /* characters which might cause a word wrap */
+	int wrapcolumn; /* wrap lines at minimum of window width and wrapcolumn (if != 0) */
+	int wrapcol;    /* used while drawing view content, column where word wrap might happen */
+	bool prevch_breakat; /* used while drawing view content, previous char is part of breakat */
 };
 
 static const SyntaxSymbol symbols_none[] = {
@@ -109,6 +113,7 @@ static bool view_viewport_up(View *view, int n);
 static bool view_viewport_down(View *view, int n);
 
 static void view_clear(View *view);
+static bool view_add_cell(View *view, const Cell *cell);
 static bool view_addch(View *view, Cell *cell);
 static void selection_free(Selection*);
 /* set/move current cursor position to a given (line, column) pair */
@@ -156,6 +161,8 @@ static void view_clear(View *view) {
 	view->bottomline->next = NULL;
 	view->line = view->topline;
 	view->col = 0;
+	view->wrapcol = 0;
+	view->prevch_breakat = false;
 	if (view->ui)
 		view->cell_blank.style = view->ui->style_get(view->ui, UI_STYLE_DEFAULT);
 }
@@ -164,24 +171,57 @@ Filerange view_viewport_get(View *view) {
 	return (Filerange){ .start = view->start, .end = view->end };
 }
 
-static bool view_add_cell(View *view, const Cell *cell) {
-	size_t lineno = view->line->lineno;
+static int view_max_text_width(const View *view) {
+	if (view->wrapcolumn > 0)
+		return MIN(view->wrapcolumn, view->width);
+	return view->width;
+}
+
+static void view_wrap_line(View *view) {
+	Line *wrapped_line = view->line;
+	int col = view->col;
+	int wrapcol = (view->wrapcol > 0) ? view->wrapcol : view->col;
+
+	view->line = view->line->next;
+	view->col = 0;
+	view->wrapcol = 0;
 
-	if (view->col + cell->width > view->width) {
-		for (int i = view->col; i < view->width; i++)
-			view->line->cells[i] = view->cell_blank;
-		view->line = view->line->next;
-		view->col = 0;
+	if (view->line) {
+		view->line->lineno = wrapped_line->lineno;
+		/* move extra cells to the next line */
+		for (int i = wrapcol; i < col; ++i) {
+			const Cell *cell = &wrapped_line->cells[i];
+			view->line->width += cell->width;
+			view->line->len += cell->len;
+			view->line->cells[view->col++] = *cell;
+		}
 	}
 
-	if (!view->line)
-		return false;
+	/* clear remaining cells on line */
+	for (int i = wrapcol; i < view->width; ++i) {
+		if (i < col) {
+			wrapped_line->width -= wrapped_line->cells[i].width;
+			wrapped_line->len -= wrapped_line->cells[i].len;
+		}
+		wrapped_line->cells[i] = view->cell_blank;
+	}
+}
+
+static bool view_add_cell(View *view, const Cell *cell) {
+	/* if the terminal is resized to a single (ASCII) char an out
+	 * of bounds write could be performed for a wide char. this can
+	 * be caught by iterating through the lines with view_wrap_line()
+	 * until no lines remain. usually 0 or 1 iterations.
+	 */
+	while (view->col + cell->width > view_max_text_width(view)) {
+		view_wrap_line(view);
+		if (!view->line)
+			return false;
+	}
 
 	view->line->width += cell->width;
 	view->line->len += cell->len;
-	view->line->lineno = lineno;
-	view->line->cells[view->col] = *cell;
-	view->col++;
+	view->line->cells[view->col++] = *cell;
 	/* set cells of a character which uses multiple columns */
 	for (int i = 1; i < cell->width; i++)
 		view->line->cells[view->col++] = cell_unused;
@@ -193,7 +233,6 @@ static bool view_expand_tab(View *view, Cell *cell) {
 
 	int displayed_width = view->tabwidth - (view->col % view->tabwidth);
 	for (int w = 0; w < displayed_width; ++w) {
-
 		int t = (w == 0) ? SYNTAX_SYMBOL_TAB : SYNTAX_SYMBOL_TAB_FILL;
 		const char *symbol = view->symbols[t]->symbol;
 		strncpy(cell->data, symbol, sizeof(cell->data) - 1);
@@ -208,22 +247,18 @@ static bool view_expand_tab(View *view, Cell *cell) {
 }
 
 static bool view_expand_newline(View *view, Cell *cell) {
+	size_t lineno = view->line->lineno;
 	const char *symbol = view->symbols[SYNTAX_SYMBOL_EOL]->symbol;
+
 	strncpy(cell->data, symbol, sizeof(cell->data) - 1);
 	cell->width = 1;
-
 	if (!view_add_cell(view, cell))
 		return false;
 
-	for (int i = view->col; i < view->width; ++i)
-		view->line->cells[i] = view->cell_blank;
-
-	size_t lineno = view->line->lineno;
-	view->line = view->line->next;
-	view->col = 0;
+	view->wrapcol = 0;
+	view_wrap_line(view);
 	if (view->line)
 		view->line->lineno = lineno + 1;
-
 	return true;
 }
 
@@ -232,9 +267,15 @@ static bool view_addch(View *view, Cell *cell) {
 	if (!view->line)
 		return false;
 
-	unsigned char ch = (unsigned char)cell->data[0];
+	bool ch_breakat = (cell->data[0] != 0) && strstr(view->breakat, cell->data);
+	if (view->prevch_breakat && !ch_breakat) {
+		/* this is a good place to wrap line if needed */
+		view->wrapcol = view->col;
+	}
+	view->prevch_breakat = ch_breakat;
 	cell->style = view->cell_blank.style;
 
+	unsigned char ch = (unsigned char)cell->data[0];
 	switch (ch) {
 	case '\t':
 		return view_expand_tab(view, cell);
@@ -493,6 +534,7 @@ void view_free(View *view) {
 		selection_free(view->selections);
 	free(view->textbuf);
 	free(view->lines);
+	free(view->breakat);
 	free(view);
 }
 
@@ -508,27 +550,27 @@ View *view_new(Text *text) {
 	View *view = calloc(1, sizeof(View));
 	if (!view)
 		return NULL;
-	view->text = text;
-	if (!view_selections_new(view, 0)) {
-		view_free(view);
-		return NULL;
-	}
 
+	view->text = text;
+	view->tabwidth = 8;
+	view->breakat = strdup("");
+	view->wrapcolumn = 0;
 	view->cell_blank = (Cell) {
 		.width = 0,
 		.len = 0,
 		.data = " ",
 	};
-	view->tabwidth = 8;
 	view_options_set(view, 0);
 
-	if (!view_resize(view, 1, 1)) {
+	if (!view->breakat ||
+	    !view_selections_new(view, 0) ||
+	    !view_resize(view, 1, 1))
+	{
 		view_free(view);
 		return NULL;
 	}
 
 	view_cursor_to(view, 0);
-
 	return view;
 }
 
@@ -863,6 +905,20 @@ int view_colorcolumn_get(View *view) {
 	return view->colorcolumn;
 }
 
+void view_wrapcolumn_set(View *view, int col) {
+	if (col >= 0)
+		view->wrapcolumn = col;
+}
+
+bool view_breakat_set(View *view, const char *breakat) {
+	char *copy = strdup(breakat);
+	if (!copy)
+		return false;
+	free(view->breakat);
+	view->breakat = copy;
+	return true;
+}
+
 size_t view_screenline_goto(View *view, int n) {
 	size_t pos = view->start;
 	for (Line *line = view->topline; --n > 0 && line != view->lastline; line = line->next)