add support for TABs in Listings, fileformat change, fixes http://bugzilla.lyx.org/show_bug.cgi?id=3629 , patch by Vincent, lyx2lyx and UI stuff by me

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@26647 a592a061-630c-0410-9148-cb99ea01b6c8

development/FORMAT

@@ -1,6 +1,9 @@
 LyX file-format changes
 -----------------------
 
+2008-09-30 Uwe Stöhr <uwestoehr@web.de>
+	* Format incremented to 341: support for TABs in listings".
+
 2008-08-01 José Matos <jamatos@fc.up.pt>
 	* Format incremented to 340: move empty layouts to "Plain Layout".
 
@@ -1023,5 +1026,3 @@ renamed as "size_kind" and "lyxsize_kind" respectively.
 
  \end_inset
 
-
-

lib/lyx2lyx/lyx_1_6.py

@@ -2906,6 +2906,37 @@ def add_plain_layout(document):
             document.body[i] = "\\begin_layout Plain Layout"
         i += 1
 
+
+def revert_tabulators(document):
+    "Revert tabulators to 4 spaces"
+    i = 0
+    while True:
+        i = find_token(document.body, "\t", i)
+        if i == -1:
+            return
+        document.body[i] = document.body[i].replace("\t", "    ")
+        i += 1
+
+
+def revert_tabsize(document):
+    "Revert the tabsize parameter of listings"
+    i = 0
+    j = 0
+    while True:
+        # either it is the only parameter
+        i = find_token(document.body, 'lstparams "tabsize=4"', i)
+        if i != -1:
+            del document.body[i]
+        # or the last one
+        j = find_token(document.body, "lstparams", j)
+        if j == -1:
+            return
+        pos = document.body[j].find(",tabsize=")
+        document.body[j] = document.body[j][:pos] + '"'
+        i += 1
+        j += 1
+
+
 ##
 # Conversion hub
 #
@@ -2974,10 +3005,12 @@ convert = [[277, [fix_wrong_tables]],
            [337, [convert_display_enum]],
            [338, []],
            [339, []],
-           [340, [add_plain_layout]]
+           [340, [add_plain_layout]],
+           [341, []]
           ]
 
-revert =  [[339, []],
+revert =  [[340, [revert_tabulators, revert_tabsize]],
+           [339, []],
            [338, [revert_removed_modules]],
            [337, [revert_polytonicgreek]],
            [336, [revert_display_enum]],

src/Buffer.cpp

@@ -115,7 +115,7 @@ namespace os = support::os;
 
 namespace {
 
-int const LYX_FORMAT = 340; //jamatos: add plain layout
+int const LYX_FORMAT = 341; //uwestoehr: TAB support for listings
 
 typedef map<string, bool> DepClean;
 typedef map<docstring, pair<InsetLabel const *, Buffer::References> > RefCache;
@@ -619,11 +619,8 @@ void Buffer::insertStringAsLines(ParagraphList & pars,
 				++pos;
 				space_inserted = true;
 			} else {
-				const pos_type n = 8 - pos % 8;
+				par.insertChar(pos, *cit, font, params().trackChanges);
-				for (pos_type i = 0; i < n; ++i) {
+				++pos;
-					par.insertChar(pos, ' ', font, params().trackChanges);
-					++pos;
-				}
 				space_inserted = true;
 			}
 		} else if (!isPrintable(*cit)) {

src/Lexer.cpp

@@ -499,7 +499,7 @@ bool Lexer::Pimpl::nextToken()
 		char cc = 0;
 		is.get(cc);
 		c = cc;
-		if (c >= ' ' && is) {
+		if ((c >= ' ' || c == '\t') && is) {
 			buff.clear();
 
 			if (c == '\\') { // first char == '\\'
@@ -513,7 +513,7 @@ bool Lexer::Pimpl::nextToken()
 					buff.push_back(c);
 					is.get(cc);
 					c = cc;
-				} while (c >= ' ' && c != '\\' && is);
+				} while ((c >= ' ' || c == '\t') && c != '\\' && is);
 			}
 
 			if (c == '\\')

src/Paragraph.cpp

@@ -2396,7 +2396,7 @@ docstring Paragraph::asString(pos_type beg, pos_type end, int options) const
 
 	for (pos_type i = beg; i < end; ++i) {
 		char_type const c = d->text_[i];
-		if (isPrintable(c))
+		if (isPrintable(c) || c == '\t')
 			os.put(c);
 		else if (c == META_INSET && options & AS_STR_INSETS)
 			getInset(i)->textString(os);

src/ParagraphMetrics.cpp

@@ -220,6 +220,9 @@ int ParagraphMetrics::singleWidth(pos_type pos, Font const & font) const
 
 	char_type c = par_->getChar(pos);
 
+	if (c == '\t')
+		return 4 * theFontMetrics(font).width(' ');
+	
 	if (!isPrintable(c))
 		return theFontMetrics(font).width(c);
 

src/frontends/qt4/GuiListings.cpp

@@ -20,6 +20,7 @@
 #include "insets/InsetListings.h"
 #include "insets/InsetListingsParams.h"
 
+#include "support/convert.h"
 #include "support/debug.h"
 #include "support/gettext.h"
 #include "support/lstrings.h"
@@ -198,6 +199,8 @@ GuiListings::GuiListings(GuiView & lv)
 		this, SLOT(change_adaptor()));
 	connect(spaceInStringCB, SIGNAL(clicked()),
 		this, SLOT(change_adaptor()));
+	connect(tabsizeSB, SIGNAL(valueChanged(int)),
+		this, SLOT(change_adaptor()));
 	connect(extendedcharsCB, SIGNAL(clicked()),
 		this, SLOT(change_adaptor()));
 
@@ -296,6 +299,7 @@ string GuiListings::construct_params()
 		basicstyle += "\\" + fontstyle;
 	bool breakline = breaklinesCB->isChecked();
 	bool space = spaceCB->isChecked();
+	int tabsize = tabsizeSB->value();
 	bool spaceInString = spaceInStringCB->isChecked();
 	bool extendedchars = extendedcharsCB->isChecked();
 	string extra = fromqstr(listingsED->toPlainText());
@@ -331,6 +335,8 @@ string GuiListings::construct_params()
 		par.addParam("showspaces", "true");
 	if (!spaceInString)
 		par.addParam("showstringspaces", "false");
+	if (tabsize != 8)
+		par.addParam("tabsize", convert<string>(tabsize));
 	if (extendedchars)
 		par.addParam("extendedchars", "true");
 	par.addParams(extra);
@@ -456,6 +462,7 @@ void GuiListings::updateContents()
 	breaklinesCB->setChecked(false);
 	spaceCB->setChecked(false);
 	spaceInStringCB->setChecked(true);
+	tabsizeSB->setValue(8);
 	extendedcharsCB->setChecked(false);
 
 	// set values from param string
@@ -583,6 +590,9 @@ void GuiListings::updateContents()
 		} else if (prefixIs(*it, "showstringspaces=")) {
 			spaceInStringCB->setChecked(contains(*it, "true"));
 			*it = "";
+		} else if (prefixIs(*it, "tabsize=")) {
+			tabsizeSB->setValue(convert<int>(plainParam(it->substr(8))));
+			*it = "";
 		} else if (prefixIs(*it, "extendedchars=")) {
 			extendedcharsCB->setChecked(contains(*it, "true"));
 			*it = "";

src/frontends/qt4/ui/ListingsUi.ui

@@ -8,8 +8,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>612</width>
+    <width>654</width>
-    <height>317</height>
+    <height>349</height>
    </rect>
   </property>
   <property name="windowTitle" >
@@ -28,9 +28,7 @@
    <item row="0" column="0" >
     <widget class="QTabWidget" name="listingsTW" >
      <property name="sizePolicy" >
-      <sizepolicy>
+      <sizepolicy vsizetype="MinimumExpanding" hsizetype="MinimumExpanding" >
-       <hsizetype>3</hsizetype>
-       <vsizetype>3</vsizetype>
        <horstretch>0</horstretch>
        <verstretch>0</verstretch>
       </sizepolicy>
@@ -49,150 +47,6 @@
        <property name="spacing" >
         <number>6</number>
        </property>
-       <item rowspan="2" row="0" column="2" >
-        <widget class="QGroupBox" name="basicstyleGB" >
-         <property name="title" >
-          <string>Style</string>
-         </property>
-         <layout class="QGridLayout" >
-          <property name="margin" >
-           <number>9</number>
-          </property>
-          <property name="spacing" >
-           <number>6</number>
-          </property>
-          <item row="0" column="1" >
-           <widget class="QComboBox" name="fontsizeCO" >
-            <property name="sizePolicy" >
-             <sizepolicy>
-              <hsizetype>7</hsizetype>
-              <vsizetype>0</vsizetype>
-              <horstretch>0</horstretch>
-              <verstretch>0</verstretch>
-             </sizepolicy>
-            </property>
-            <property name="toolTip" >
-             <string>The content's base font size</string>
-            </property>
-            <property name="editable" >
-             <bool>false</bool>
-            </property>
-            <property name="autoCompletion" >
-             <bool>true</bool>
-            </property>
-            <property name="duplicatesEnabled" >
-             <bool>false</bool>
-            </property>
-           </widget>
-          </item>
-          <item row="0" column="0" >
-           <widget class="QLabel" name="fontsize_label_3" >
-            <property name="text" >
-             <string>F&amp;ont size:</string>
-            </property>
-            <property name="wordWrap" >
-             <bool>false</bool>
-            </property>
-            <property name="buddy" >
-             <cstring>fontsizeCO</cstring>
-            </property>
-           </widget>
-          </item>
-          <item row="1" column="1" >
-           <widget class="QComboBox" name="fontstyleCO" >
-            <property name="sizePolicy" >
-             <sizepolicy>
-              <hsizetype>7</hsizetype>
-              <vsizetype>0</vsizetype>
-              <horstretch>0</horstretch>
-              <verstretch>0</verstretch>
-             </sizepolicy>
-            </property>
-            <property name="toolTip" >
-             <string>The content's base font style</string>
-            </property>
-            <property name="editable" >
-             <bool>false</bool>
-            </property>
-            <property name="autoCompletion" >
-             <bool>true</bool>
-            </property>
-            <property name="duplicatesEnabled" >
-             <bool>false</bool>
-            </property>
-           </widget>
-          </item>
-          <item row="1" column="0" >
-           <widget class="QLabel" name="fontstyle_label_3" >
-            <property name="text" >
-             <string>Font Famil&amp;y:</string>
-            </property>
-            <property name="wordWrap" >
-             <bool>false</bool>
-            </property>
-            <property name="buddy" >
-             <cstring>fontstyleCO</cstring>
-            </property>
-           </widget>
-          </item>
-          <item row="5" column="0" colspan="2" >
-           <widget class="QCheckBox" name="extendedcharsCB" >
-            <property name="enabled" >
-             <bool>true</bool>
-            </property>
-            <property name="toolTip" >
-             <string>Use extended character table</string>
-            </property>
-            <property name="text" >
-             <string>&amp;Extended character table</string>
-            </property>
-            <property name="shortcut" >
-             <number>276824133</number>
-            </property>
-           </widget>
-          </item>
-          <item row="4" column="0" colspan="2" >
-           <widget class="QCheckBox" name="spaceInStringCB" >
-            <property name="toolTip" >
-             <string>Make spaces in strings visible by a special symbol</string>
-            </property>
-            <property name="text" >
-             <string>Space i&amp;n string as symbol</string>
-            </property>
-            <property name="shortcut" >
-             <number>276824147</number>
-            </property>
-           </widget>
-          </item>
-          <item row="3" column="0" colspan="2" >
-           <widget class="QCheckBox" name="spaceCB" >
-            <property name="toolTip" >
-             <string>Make spaces visible by a special symbol</string>
-            </property>
-            <property name="text" >
-             <string>S&amp;pace as symbol</string>
-            </property>
-            <property name="shortcut" >
-             <number>276824147</number>
-            </property>
-           </widget>
-          </item>
-          <item row="2" column="0" colspan="2" >
-           <widget class="QCheckBox" name="breaklinesCB" >
-            <property name="toolTip" >
-             <string>Break lines longer than the linewidth</string>
-            </property>
-            <property name="text" >
-             <string>&amp;Break long lines</string>
-            </property>
-            <property name="shortcut" >
-             <number>276824130</number>
-            </property>
-           </widget>
-          </item>
-         </layout>
-        </widget>
-       </item>
        <item row="0" column="0" >
         <widget class="QGroupBox" name="placementGB" >
          <property name="title" >
@@ -285,9 +139,7 @@
           <item row="2" column="1" >
            <widget class="QComboBox" name="numberFontSizeCO" >
             <property name="sizePolicy" >
-             <sizepolicy>
+             <sizepolicy vsizetype="Fixed" hsizetype="Expanding" >
-              <hsizetype>7</hsizetype>
-              <vsizetype>0</vsizetype>
               <horstretch>0</horstretch>
               <verstretch>0</verstretch>
              </sizepolicy>
@@ -478,6 +330,175 @@
            </widget>
           </item>
          </layout>
+         <zorder>numberfontsizeL_2</zorder>
+         <zorder>lastlineLE</zorder>
+         <zorder>firstlineLE</zorder>
+         <zorder>numberfontsizeL_3</zorder>
+         <zorder>basicstyleGB</zorder>
+        </widget>
+       </item>
+       <item rowspan="2" row="0" column="2" >
+        <widget class="QGroupBox" name="basicstyleGB" >
+         <property name="title" >
+          <string>Style</string>
+         </property>
+         <layout class="QGridLayout" >
+          <property name="sizeConstraint" >
+           <enum>QLayout::SetDefaultConstraint</enum>
+          </property>
+          <property name="margin" >
+           <number>9</number>
+          </property>
+          <property name="spacing" >
+           <number>6</number>
+          </property>
+          <item row="0" column="0" >
+           <widget class="QLabel" name="fontsize_label_3" >
+            <property name="text" >
+             <string>F&amp;ont size:</string>
+            </property>
+            <property name="wordWrap" >
+             <bool>false</bool>
+            </property>
+            <property name="buddy" >
+             <cstring>fontsizeCO</cstring>
+            </property>
+           </widget>
+          </item>
+          <item row="0" column="1" >
+           <widget class="QComboBox" name="fontsizeCO" >
+            <property name="sizePolicy" >
+             <sizepolicy vsizetype="Fixed" hsizetype="Expanding" >
+              <horstretch>0</horstretch>
+              <verstretch>0</verstretch>
+             </sizepolicy>
+            </property>
+            <property name="toolTip" >
+             <string>The content's base font size</string>
+            </property>
+            <property name="editable" >
+             <bool>false</bool>
+            </property>
+            <property name="autoCompletion" >
+             <bool>true</bool>
+            </property>
+            <property name="duplicatesEnabled" >
+             <bool>false</bool>
+            </property>
+           </widget>
+          </item>
+          <item row="1" column="0" >
+           <widget class="QLabel" name="fontstyle_label_3" >
+            <property name="text" >
+             <string>Font Famil&amp;y:</string>
+            </property>
+            <property name="wordWrap" >
+             <bool>false</bool>
+            </property>
+            <property name="buddy" >
+             <cstring>fontstyleCO</cstring>
+            </property>
+           </widget>
+          </item>
+          <item row="1" column="1" >
+           <widget class="QComboBox" name="fontstyleCO" >
+            <property name="sizePolicy" >
+             <sizepolicy vsizetype="Fixed" hsizetype="Expanding" >
+              <horstretch>0</horstretch>
+              <verstretch>0</verstretch>
+             </sizepolicy>
+            </property>
+            <property name="toolTip" >
+             <string>The content's base font style</string>
+            </property>
+            <property name="editable" >
+             <bool>false</bool>
+            </property>
+            <property name="autoCompletion" >
+             <bool>true</bool>
+            </property>
+            <property name="duplicatesEnabled" >
+             <bool>false</bool>
+            </property>
+           </widget>
+          </item>
+          <item row="2" column="0" colspan="2" >
+           <widget class="QCheckBox" name="breaklinesCB" >
+            <property name="toolTip" >
+             <string>Break lines longer than the linewidth</string>
+            </property>
+            <property name="text" >
+             <string>&amp;Break long lines</string>
+            </property>
+            <property name="shortcut" >
+             <number>276824130</number>
+            </property>
+           </widget>
+          </item>
+          <item row="3" column="0" colspan="2" >
+           <widget class="QCheckBox" name="spaceCB" >
+            <property name="toolTip" >
+             <string>Make spaces visible by a special symbol</string>
+            </property>
+            <property name="text" >
+             <string>S&amp;pace as symbol</string>
+            </property>
+            <property name="shortcut" >
+             <number>276824147</number>
+            </property>
+           </widget>
+          </item>
+          <item row="5" column="0" colspan="2" >
+           <widget class="QCheckBox" name="spaceInStringCB" >
+            <property name="toolTip" >
+             <string>Make spaces in strings visible by a special symbol</string>
+            </property>
+            <property name="text" >
+             <string>Space i&amp;n string as symbol</string>
+            </property>
+            <property name="shortcut" >
+             <number>276824147</number>
+            </property>
+           </widget>
+          </item>
+          <item row="6" column="0" >
+           <widget class="QLabel" name="tabsizeL" >
+            <property name="text" >
+             <string>Tabulator size</string>
+            </property>
+           </widget>
+          </item>
+          <item row="6" column="1" >
+           <widget class="QSpinBox" name="tabsizeSB" />
+          </item>
+          <item row="7" column="0" colspan="2" >
+           <widget class="QCheckBox" name="extendedcharsCB" >
+            <property name="enabled" >
+             <bool>true</bool>
+            </property>
+            <property name="toolTip" >
+             <string>Use extended character table</string>
+            </property>
+            <property name="text" >
+             <string>&amp;Extended character table</string>
+            </property>
+            <property name="shortcut" >
+             <number>276824133</number>
+            </property>
+           </widget>
+          </item>
+         </layout>
+         <zorder>fontsizeCO</zorder>
+         <zorder>fontsize_label_3</zorder>
+         <zorder>fontstyleCO</zorder>
+         <zorder>fontstyle_label_3</zorder>
+         <zorder>extendedcharsCB</zorder>
+         <zorder>spaceCB</zorder>
+         <zorder>breaklinesCB</zorder>
+         <zorder>label_2</zorder>
+         <zorder>tabsizeL</zorder>
+         <zorder>tabsizeSB</zorder>
+         <zorder>horizontalSpacer</zorder>
         </widget>
        </item>
       </layout>
@@ -496,9 +517,7 @@
        <item row="0" column="0" >
         <widget class="QGroupBox" name="listingsGB" >
          <property name="sizePolicy" >
-          <sizepolicy>
+          <sizepolicy vsizetype="MinimumExpanding" hsizetype="MinimumExpanding" >
-           <hsizetype>3</hsizetype>
-           <vsizetype>3</vsizetype>
            <horstretch>0</horstretch>
            <verstretch>0</verstretch>
           </sizepolicy>
@@ -535,8 +554,8 @@
                <height>16777215</height>
               </size>
              </property>
-             <property name="cursor" >
+             <property name="cursor" stdset="0" >
-              <cursor>0</cursor>
+              <cursorShape>ArrowCursor</cursorShape>
              </property>
              <property name="acceptDrops" >
               <bool>false</bool>
@@ -556,9 +575,7 @@
             </widget>
             <widget class="QTextEdit" name="listingsED" >
              <property name="sizePolicy" >
-              <sizepolicy>
+              <sizepolicy vsizetype="MinimumExpanding" hsizetype="MinimumExpanding" >
-               <hsizetype>3</hsizetype>
-               <vsizetype>3</vsizetype>
                <horstretch>0</horstretch>
                <verstretch>0</verstretch>
               </sizepolicy>
@@ -578,12 +595,12 @@
    </item>
    <item row="1" column="0" >
     <layout class="QHBoxLayout" >
-     <property name="margin" >
-      <number>0</number>
-     </property>
      <property name="spacing" >
       <number>6</number>
      </property>
+     <property name="margin" >
+      <number>0</number>
+     </property>
      <item>
       <spacer>
        <property name="orientation" >
@@ -592,7 +609,7 @@
        <property name="sizeType" >
         <enum>QSizePolicy::Expanding</enum>
        </property>
-       <property name="sizeHint" >
+       <property name="sizeHint" stdset="0" >
         <size>
          <width>221</width>
          <height>27</height>

src/insets/InsetListings.cpp

@@ -33,6 +33,7 @@
 #include "support/docstream.h"
 #include "support/gettext.h"
 #include "support/lstrings.h"
+#include "support/lassert.h"
 
 #include "frontends/alert.h"
 #include "frontends/Application.h"
@@ -289,6 +290,87 @@ void InsetListings::doDispatch(Cursor & cur, FuncRequest & cmd)
 	case LFUN_INSET_DIALOG_UPDATE:
 		cur.bv().updateDialog("listings", params2string(params()));
 		break;
+	case LFUN_CELL_FORWARD:
+		if (cur.selection()) {
+			// If there is a selection, a tab is inserted at the
+			// beginning of each paragraph.
+			cur.recordUndoSelection();
+			pit_type const pit_end = cur.selEnd().pit();
+			for (pit_type pit = cur.selBegin().pit(); pit <= pit_end; pit++) {
+				LASSERT(pit < paragraphs().size(), /**/);
+				paragraphs()[pit].insertChar(0, '\t', 
+					buffer().params().trackChanges);
+				// Update the selection pos to make sure the selection does not
+				// change as the inserted tab will increase the logical pos.
+				if (cur.anchor_.pit() == pit)
+					cur.anchor_.forwardPos();
+				if (cur.pit() == pit)
+					cur.forwardPos();
+			}
+			cur.finishUndo();
+		} else {
+			// Maybe we shouldn't allow tabs within a line, because they
+			// are not (yet) aligned as one might do expect.
+			cur.recordUndo();
+			cur.insert(from_ascii("\t"));
+			cur.finishUndo();
+		}
+		break;
+	case LFUN_CELL_BACKWARD:
+		if (cur.selection()) {
+			// If there is a selection, a tab (if present) is removed from
+			// the beginning of each paragraph.
+			cur.recordUndoSelection();
+			pit_type const pit_end = cur.selEnd().pit();
+			for (pit_type pit = cur.selBegin().pit(); pit <= pit_end; pit++) {
+				LASSERT( pit < paragraphs().size(), /**/ );
+				Paragraph & par = paragraphs()[pit];
+				if (par.getChar(0) == '\t') {
+					if (cur.pit() == pit)
+						cur.posBackward();
+					if (cur.anchor_.pit() == pit && cur.anchor_.pos() > 0 )
+						cur.anchor_.backwardPos();
+
+					par.eraseChar(0, buffer().params().trackChanges);
+				} else 
+					// If no tab was present, try to remove up to four spaces.
+					for (int n_spaces = 0;
+						par.getChar(0) == ' ' && n_spaces < 4; ++n_spaces) {
+							if (cur.pit() == pit)
+								cur.posBackward();
+							if (cur.anchor_.pit() == pit && cur.anchor_.pos() > 0 )
+								cur.anchor_.backwardPos();
+
+							par.eraseChar(0, buffer().params().trackChanges);
+					}
+			}
+			cur.finishUndo();
+		} else {
+			// If there is no selection, try to remove a tab or some spaces 
+			// before the position of the cursor.
+			LASSERT(cur.pit() >= 0 && cur.pit() < paragraphs().size(), /**/);
+
+			Paragraph & par = paragraphs()[cur.pit()];
+			pos_type const pos = cur.pos();
+
+			if (pos == 0)
+				break;
+
+			char_type const c = par.getChar(pos - 1);
+			cur.recordUndo();
+			if (c == '\t') {
+				cur.posBackward();
+				par.eraseChar(cur.pos(), buffer().params().trackChanges);
+			} else
+				for (int n_spaces = 0; cur.pos() > 0
+					&& par.getChar(cur.pos() - 1) == ' ' && n_spaces < 4;
+					++n_spaces) {
+						cur.posBackward();
+						par.eraseChar(cur.pos(), buffer().params().trackChanges);
+				}
+				cur.finishUndo();
+		}
+		break;
 	default:
 		InsetCollapsable::doDispatch(cur, cmd);
 		break;
@@ -307,6 +389,10 @@ bool InsetListings::getStatus(Cursor & cur, FuncRequest const & cmd,
 		case LFUN_CAPTION_INSERT:
 			status.setEnabled(!params().isInline());
 			return true;
+			case LFUN_CELL_BACKWARD:
+			case LFUN_CELL_FORWARD:
+				status.setEnabled(true);
+				return true;
 		default:
 			return InsetCollapsable::getStatus(cur, cmd, status);
 	}

src/rowpainter.cpp

@@ -246,6 +246,7 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
 	// selected text?
 	bool const selection = pos >= row_.sel_beg && pos < row_.sel_end;
 
+	char_type prev_char = ' ';
 	// collect as much similar chars as we can
 	for (++vpos ; vpos < end ; ++vpos) {
 		pos = bidi_.vis2log(vpos);
@@ -264,6 +265,11 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
 
 		char_type c = par_.getChar(pos);
 
+		if (c == '\t' || prev_char == '\t') {
+			prev_char = c;
+			break;
+		}
+
 		if (!isPrintableNonspace(c))
 			break;
 
@@ -308,6 +314,9 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
 
 	docstring s(&str[0], str.size());
 
+	if (s[0] == '\t')
+		s.replace(0,1,from_ascii("    "));
+
 	if (!selection && !change_running.changed()) {
 		x_ += pi_.pain.text(int(x_), yo_, s, font);
 		return;