Fix #12976: Incorrect widget rect scrolling for RTL languages. (#12978)

Industry directory, AS/GS and Textfile window did not consider RTL when applying horizontal scrolling.

src/industry_gui.cpp

@@ -1712,8 +1712,7 @@ public:
 
 				AutoRestoreBackup dpi_backup(_cur_dpi, &tmp_dpi);
 
-				ir.left -= this->hscroll->GetPosition();
-				ir.right += this->hscroll->GetCapacity() - this->hscroll->GetPosition();
+				ir = ScrollRect(ir, *this->hscroll, 1);
 
 				if (this->industries.empty()) {
 					DrawString(ir, STR_INDUSTRY_DIRECTORY_NONE);

src/script/script_gui.cpp

@@ -910,7 +910,7 @@ struct ScriptDebugWindow : public Window {
 
 		AutoRestoreBackup dpi_backup(_cur_dpi, &tmp_dpi);
 
-		fr.left -= this->hscroll->GetPosition();
+		fr = ScrollRect(fr, *this->hscroll, 1);
 
 		auto [first, last] = this->vscroll->GetVisibleRangeIterators(log);
 		for (auto it = first; it != last; ++it) {

src/textfile_gui.cpp

@@ -156,7 +156,7 @@ void TextfileWindow::SetupScrollbars(bool force_reflow)
 	} else {
 		uint height = force_reflow ? this->ReflowContent() : this->GetContentHeight();
 		this->vscroll->SetCount(ClampTo<uint16_t>(height));
-		this->hscroll->SetCount(this->max_length + WidgetDimensions::scaled.frametext.Horizontal());
+		this->hscroll->SetCount(this->max_length);
 	}
 
 	this->SetWidgetDisabledState(WID_TF_HSCROLLBAR, IsWidgetLowered(WID_TF_WRAPTEXT));
@@ -568,6 +568,9 @@ void TextfileWindow::AfterLoadMarkdown()
 	/* Draw content (now coordinates given to DrawString* are local to the new clipping region). */
 	fr = fr.Translate(-fr.left, -fr.top);
 	int line_height = GetCharacterHeight(FS_MONO);
+
+	if (!IsWidgetLowered(WID_TF_WRAPTEXT)) fr = ScrollRect(fr, *this->hscroll, 1);
+
 	int pos = this->vscroll->GetPosition();
 	int cap = this->vscroll->GetCapacity();
 
@@ -577,9 +580,9 @@ void TextfileWindow::AfterLoadMarkdown()
 
 		int y_offset = (line.top - pos) * line_height;
 		if (IsWidgetLowered(WID_TF_WRAPTEXT)) {
-			DrawStringMultiLine(0, fr.right, y_offset, fr.bottom, line.text, line.colour, SA_TOP | SA_LEFT, false, FS_MONO);
+			DrawStringMultiLine(fr.left, fr.right, y_offset, fr.bottom, line.text, line.colour, SA_TOP | SA_LEFT, false, FS_MONO);
 		} else {
-			DrawString(-this->hscroll->GetPosition(), fr.right, y_offset, line.text, line.colour, SA_TOP | SA_LEFT, false, FS_MONO);
+			DrawString(fr.left, fr.right, y_offset, line.text, line.colour, SA_TOP | SA_LEFT, false, FS_MONO);
 		}
 	}
 }

src/widget.cpp

@@ -2401,6 +2401,35 @@ void Scrollbar::SetCapacityFromWidget(Window *w, WidgetID widget, int padding)
 	}
 }
 
+/**
+ * Apply 'scroll' to a rect to be drawn in.
+ * @param r Rect to be 'scrolled'.
+ * @param sb The scrollbar affecting the scroll.
+ * @param resize_step Resize step of the widget/scrollbar (1 if the scrollbar is pixel-based.)
+ * @returns Scrolled rect.
+ */
+Rect ScrollRect(Rect r, const Scrollbar &sb, int resize_step)
+{
+	const int count = sb.GetCount() * resize_step;
+	const int position = sb.GetPosition() * resize_step;
+
+	if (sb.IsVertical()) {
+		r.top -= position;
+		r.bottom = r.top + count;
+	} else {
+		bool rtl = _current_text_dir == TD_RTL;
+		if (rtl) {
+			r.right += position;
+			r.left = r.right - count;
+		} else {
+			r.left -= position;
+			r.right = r.left + count;
+		}
+	}
+
+	return r;
+}
+
 /**
  * Scrollbar widget.
  * @param tp     Scrollbar type. (horizontal/vertical)

src/window_gui.h

@@ -1051,5 +1051,6 @@ extern SpecialMouseMode _special_mouse_mode;
 void SetFocusedWindow(Window *w);
 
 void ScrollbarClickHandler(Window *w, NWidgetCore *nw, int x, int y);
+Rect ScrollRect(Rect r, const Scrollbar &sb, int resize_step = 1);
 
 #endif /* WINDOW_GUI_H */