From e8f134e9a1567775377c66c8bd34825380c328a6 Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Thu, 29 Jul 2021 13:12:16 +1000
Subject: Add SC_ELEMENT_HIDDEN_LINE to show where lines are hidden.

---
 doc/ScintillaDoc.html     | 13 +++++++++++++
 doc/ScintillaHistory.html |  1 +
 include/Scintilla.h       |  1 +
 include/Scintilla.iface   |  1 +
 include/ScintillaTypes.h  |  1 +
 src/EditView.cxx          | 11 +++++++++++
 6 files changed, 28 insertions(+)

diff --git a/doc/ScintillaDoc.html b/doc/ScintillaDoc.html
index 511632937..b38cfb83c 100644
--- a/doc/ScintillaDoc.html
+++ b/doc/ScintillaDoc.html
@@ -3504,6 +3504,14 @@ struct Sci_TextToFind {
            <td></td>
            <td>Colour of fold lines</td>
          </tr>
+         <tr>
+           <th align="left"><code>SC_ELEMENT_HIDDEN_LINE</code></th>
+           <td>81</td>
+           <td>Translucent</td>
+           <td>All</td>
+           <td></td>
+           <td>Colour of line drawn to show there are lines hidden at that point</td>
+         </tr>
        </tbody>
      </table>
 
@@ -7008,6 +7016,7 @@ sptr_t CallScintilla(unsigned int iMessage, uptr_t wParam, sptr_t lParam){
      <a class="message" href="#SCI_DOCLINEFROMVISIBLE">SCI_DOCLINEFROMVISIBLE(line displayLine) &rarr; line</a><br />
      <a class="message" href="#SCI_SHOWLINES">SCI_SHOWLINES(line lineStart, line lineEnd)</a><br />
      <a class="message" href="#SCI_HIDELINES">SCI_HIDELINES(line lineStart, line lineEnd)</a><br />
+     <a class="element" href="#SC_ELEMENT_HIDDEN_LINE">SC_ELEMENT_HIDDEN_LINE : colouralpha</a><br />
      <a class="message" href="#SCI_GETLINEVISIBLE">SCI_GETLINEVISIBLE(line line) &rarr; bool</a><br />
      <a class="message" href="#SCI_GETALLLINESVISIBLE">SCI_GETALLLINESVISIBLE &rarr; bool</a><br />
      <a class="message" href="#SCI_SETFOLDLEVEL">SCI_SETFOLDLEVEL(line line, int level)</a><br />
@@ -7059,10 +7068,14 @@ sptr_t CallScintilla(unsigned int iMessage, uptr_t wParam, sptr_t lParam){
 
     <p><b id="SCI_SHOWLINES">SCI_SHOWLINES(line lineStart, line lineEnd)</b><br />
      <b id="SCI_HIDELINES">SCI_HIDELINES(line lineStart, line lineEnd)</b><br />
+     <b id="SC_ELEMENT_HIDDEN_LINE">SC_ELEMENT_HIDDEN_LINE : colouralpha</b><br />
      <b id="SCI_GETLINEVISIBLE">SCI_GETLINEVISIBLE(line line) &rarr; bool</b><br />
      <b id="SCI_GETALLLINESVISIBLE">SCI_GETALLLINESVISIBLE &rarr; bool</b><br />
      The first two messages mark a range of lines as visible or invisible and then redraw the
     display.
+    If <a class="element" href="#SCI_SETELEMENTCOLOUR"><code>SC_ELEMENT_HIDDEN_LINE</code></a>
+    is set then a horizontal line is drawn in that colour to indicate that there are hidden lines.
+    A fold line drawn in that position overrides the hidden line indicator.
     <code>SCI_GETLINEVISIBLE</code> reports on the visible state of a line and returns 1 if it is
     visible and 0 if it is not visible.
     <code>SCI_GETALLLINESVISIBLE</code> returns 1 if all lines are visible and 0
diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index f0c6ded0b..21f44f476 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -576,6 +576,7 @@
 	</li>
 	<li>
 	Add SC_ELEMENT_FOLD_LINE to set the colour of fold lines.
+	Add SC_ELEMENT_HIDDEN_LINE to show where lines are hidden.
 	</li>
 	<li>
 	Fix display of fold lines when wrapped so they are only drawn once per line, not on each subline.
diff --git a/include/Scintilla.h b/include/Scintilla.h
index 3af22dfc5..3a6e301b3 100644
--- a/include/Scintilla.h
+++ b/include/Scintilla.h
@@ -292,6 +292,7 @@ typedef sptr_t (*SciFnDirectStatus)(sptr_t ptr, unsigned int iMessage, uptr_t wP
 #define SC_ELEMENT_HOT_SPOT_ACTIVE 70
 #define SC_ELEMENT_HOT_SPOT_ACTIVE_BACK 71
 #define SC_ELEMENT_FOLD_LINE 80
+#define SC_ELEMENT_HIDDEN_LINE 81
 #define SCI_SETELEMENTCOLOUR 2753
 #define SCI_GETELEMENTCOLOUR 2754
 #define SCI_RESETELEMENTCOLOUR 2755
diff --git a/include/Scintilla.iface b/include/Scintilla.iface
index d8a1bdec1..837e4d841 100644
--- a/include/Scintilla.iface
+++ b/include/Scintilla.iface
@@ -698,6 +698,7 @@ val SC_ELEMENT_WHITE_SPACE_BACK=61
 val SC_ELEMENT_HOT_SPOT_ACTIVE=70
 val SC_ELEMENT_HOT_SPOT_ACTIVE_BACK=71
 val SC_ELEMENT_FOLD_LINE=80
+val SC_ELEMENT_HIDDEN_LINE=81
 
 # Set the colour of an element. Translucency (alpha) may or may not be significant
 # and this may depend on the platform. The alpha byte should commonly be 0xff for opaque.
diff --git a/include/ScintillaTypes.h b/include/ScintillaTypes.h
index ab4a55131..910cd5ec8 100644
--- a/include/ScintillaTypes.h
+++ b/include/ScintillaTypes.h
@@ -181,6 +181,7 @@ enum class Element {
 	HotSpotActive = 70,
 	HotSpotActiveBack = 71,
 	FoldLine = 80,
+	HiddenLine = 81,
 };
 
 enum class Layer {
diff --git a/src/EditView.cxx b/src/EditView.cxx
index 7eea729fd..e32e791ec 100644
--- a/src/EditView.cxx
+++ b/src/EditView.cxx
@@ -2304,6 +2304,17 @@ static void DrawFoldLines(Surface *surface, const EditModel &model, const ViewSt
 			||
 			(!expanded && (FlagSet(model.foldFlags, FoldFlag::LineAfterContracted))))) {
 			surface->FillRectangleAligned(Side(rcLine, Edge::bottom, 1.0), foldLineColour);
+			// If contracted fold line drawn then don't overwrite with hidden line
+			// as fold lines are more specific then hidden lines.
+			if (!expanded) {
+				return;
+			}
+		}
+	}
+	if (lastSubLine && model.pcs->GetVisible(line) && !model.pcs->GetVisible(line + 1)) {
+		std::optional<ColourRGBA> hiddenLineColour = vsDraw.ElementColour(Element::HiddenLine);
+		if (hiddenLineColour) {
+			surface->FillRectangleAligned(Side(rcLine, Edge::bottom, 1.0), *hiddenLineColour);
 		}
 	}
 }
-- 
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