Fix poor synchronization between mouse and keyboard modifications to the selection

Combining Shift+Up/Down (or Home/End or Page Up/Page Down) with
shift-clicking had very odd results due to that they used separate
variables to decide where to extend from (and even when only one was
used they were handled incorrectly in some cases).

Closes #1311.

Originally committed to SVN as r6355.

aegisub/src/base_grid.cpp

@@ -89,7 +89,6 @@ static inline void set_difference(const S1 &src1, const S2 &src2, D &dst) {
 BaseGrid::BaseGrid(wxWindow* parent, agi::Context *context, const wxSize& size, long style, const wxString& name)
 : wxWindow(parent, -1, wxDefaultPosition, size, style, name)
 , lineHeight(1) // non-zero to avoid div by 0
-, lastRow(-1)
 , holding(false)
 , scrollBar(new wxScrollBar(this, GRID_SCROLLBAR, wxDefaultPosition, wxDefaultSize, wxSB_VERTICAL))
 , bmp(0)
@@ -349,8 +348,6 @@ void BaseGrid::EndBatch() {
 }
 
 void BaseGrid::MakeCellVisible(int row, int col, bool center) {
-	lastRow = row;
-
 	int w = 0;
 	int h = 0;
 	GetClientSize(&w,&h);
@@ -722,51 +719,45 @@ void BaseGrid::OnMouseEvent(wxMouseEvent &event) {
 
 	// Click
 	if ((click || holding || dclick) && dlg) {
+		int old_extend = extendRow;
+		SetActiveLine(dlg);
+
 		// Toggle selected
 		if (click && ctrl && !shift && !alt) {
 			bool isSel = !!selection.count(dlg);
 			if (isSel && selection.size() == 1) return;
-			SelectRow(row,true,!isSel);
+			SelectRow(row, true, !isSel);
-			if (dlg == GetActiveLine()) {
-				SetActiveLine(GetDialogue(GetFirstSelRow()));
-			}
-			lastRow = row;
 			return;
 		}
 
 		// Normal click
 		if ((click || dclick) && !shift && !ctrl && !alt) {
-			SetActiveLine(dlg);
 			if (dclick) context->videoController->JumpToTime(dlg->Start);
-			SelectRow(row,false);
+			SelectRow(row, false);
-			lastRow = row;
 			return;
 		}
 
-		// Keep selection
+		// Change active line only
 		if (click && !shift && !ctrl && alt) {
-			SetActiveLine(dlg);
 			return;
 		}
 
 		// Block select
 		if ((click && shift && !alt) || (holding && !ctrl && !alt && !shift)) {
-			if (lastRow != -1) {
+			extendRow = old_extend;
-				// Set boundaries
+			int i1 = row;
-				int i1 = row;
+			int i2 = extendRow;
-				int i2 = lastRow;
-				if (i1 > i2) {
-					std::swap(i1, i2);
-				}
 
-				// Toggle each
+			if (i1 > i2)
-				Selection newsel;
+				std::swap(i1, i2);
-				if (ctrl) newsel = selection;
+
-				for (int i=i1;i<=i2;i++) {
+			// Toggle each
-					newsel.insert(GetDialogue(i));
+			Selection newsel;
-				}
+			if (ctrl) newsel = selection;
-				SetSelectedSet(newsel);
+			for (int i = i1; i <= i2; i++) {
+				newsel.insert(GetDialogue(i));
 			}
+			SetSelectedSet(newsel);
 			return;
 		}
 
@@ -1010,38 +1001,36 @@ void BaseGrid::OnKeyDown(wxKeyEvent &event) {
 
 	// Moving
 	if (dir) {
+		int old_extend = extendRow;
+		int next = mid(0, GetDialogueIndex(active_line) + dir * step, GetRows() - 1);
+		SetActiveLine(GetDialogue(next));
+
 		// Move selection
 		if (!ctrl && !shift && !alt) {
-			int next = mid(0, extendRow + dir * step, GetRows() - 1);
-			SetActiveLine(GetDialogue(next));
 			SelectRow(next);
 			return;
 		}
 
 		// Move active only
-		else if (alt && !shift && !ctrl) {
+		if (alt && !shift && !ctrl) {
-			int next = mid(0, GetDialogueIndex(GetActiveLine()) + dir * step, GetRows() - 1);
-			SetActiveLine(GetDialogue(next));
 			Refresh(false);
 			return;
 		}
 
 		// Shift-selection
-		else if (shift && !ctrl && !alt) {
+		if (shift && !ctrl && !alt) {
-			extendRow = mid(0, extendRow + dir * step, GetRows() - 1);
+			extendRow = old_extend;
-
 			// Set range
-			int begin = GetDialogueIndex(GetActiveLine());
+			int begin = next;
 			int end = extendRow;
-			if (end < begin) {
+			if (end < begin)
 				std::swap(begin, end);
-			}
 
 			// Select range
 			Selection newsel;
-			for (int i = begin; i <= end; i++) {
+			for (int i = begin; i <= end; i++)
 				newsel.insert(GetDialogue(i));
-			}
+
 			SetSelectedSet(newsel);
 
 			MakeCellVisible(extendRow, 0, false);

aegisub/src/base_grid.h

@@ -66,14 +66,14 @@ typedef SelectionListener<AssDialogue> SubtitleSelectionListener;
 /// DOCME
 class BaseGrid : public wxWindow, public BaseSelectionController<AssDialogue> {
 	int lineHeight;         ///< Height of a line in pixels in the current font
-	int lastRow;            ///< ?
 	bool holding;           ///< Is a drag selection in process?
 	wxFont font;            ///< Current grid font
 	wxScrollBar *scrollBar; ///< The grid's scrollbar
 	wxBitmap *bmp;          ///< Back buffer which the grid is rendered into
 	bool byFrame;           ///< Should times be displayed as frame numbers
+
 	/// Row from which the selection shrinks/grows from when selecting via the
-	/// keyboard. Equal to the active row except for when using shift+up/down.
+	/// keyboard, shift-clicking or dragging
 	int extendRow;
 
 	Selection selection;      ///< Currently selected lines