Change: Add flag to apply resize to largest resize step first.

Resize step is normally allocated equally amongst all resizable widgets.
With this flag, we allocate as much as possible from the largest
resize step first.

src/widget.cpp

@@ -1356,7 +1356,7 @@ void NWidgetHorizontal::AssignSizePosition(SizingType sizing, uint x, uint y, ui
 	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint hor_step = child_wid->GetHorizontalStepSize(sizing);
 		if (hor_step > 0) {
-			num_changing_childs++;
+			if (!(flags & NC_BIGFIRST)) num_changing_childs++;
 			biggest_stepsize = std::max(biggest_stepsize, hor_step);
 		} else {
 			child_wid->current_x = child_wid->smallest_x;
@@ -1366,6 +1366,16 @@ void NWidgetHorizontal::AssignSizePosition(SizingType sizing, uint x, uint y, ui
 		child_wid->current_y = ComputeMaxSize(child_wid->smallest_y, given_height - child_wid->padding_top - child_wid->padding_bottom, vert_step);
 	}
 
+	/* First.5 loop: count how many children are of the biggest step size. */
+	if ((flags & NC_BIGFIRST) && biggest_stepsize > 0) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+			uint hor_step = child_wid->GetHorizontalStepSize(sizing);
+			if (hor_step == biggest_stepsize) {
+				num_changing_childs++;
+			}
+		}
+	}
+
 	/* Second loop: Allocate the additional horizontal space over the resizing children, starting with the biggest resize steps. */
 	while (biggest_stepsize > 0) {
 		uint next_biggest_stepsize = 0;
@@ -1383,6 +1393,16 @@ void NWidgetHorizontal::AssignSizePosition(SizingType sizing, uint x, uint y, ui
 			next_biggest_stepsize = std::max(next_biggest_stepsize, hor_step);
 		}
 		biggest_stepsize = next_biggest_stepsize;
+
+		if (num_changing_childs == 0 && (flags & NC_BIGFIRST) && biggest_stepsize > 0) {
+			/* Second.5 loop: count how many children are of the updated biggest step size. */
+			for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+				uint hor_step = child_wid->GetHorizontalStepSize(sizing);
+				if (hor_step == biggest_stepsize) {
+					num_changing_childs++;
+				}
+			}
+		}
 	}
 	assert(num_changing_childs == 0);
 
@@ -1512,7 +1532,7 @@ void NWidgetVertical::AssignSizePosition(SizingType sizing, uint x, uint y, uint
 	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint vert_step = child_wid->GetVerticalStepSize(sizing);
 		if (vert_step > 0) {
-			num_changing_childs++;
+			if (!(flags & NC_BIGFIRST)) num_changing_childs++;
 			biggest_stepsize = std::max(biggest_stepsize, vert_step);
 		} else {
 			child_wid->current_y = child_wid->smallest_y;
@@ -1522,6 +1542,16 @@ void NWidgetVertical::AssignSizePosition(SizingType sizing, uint x, uint y, uint
 		child_wid->current_x = ComputeMaxSize(child_wid->smallest_x, given_width - child_wid->padding_left - child_wid->padding_right, hor_step);
 	}
 
+	/* First.5 loop: count how many children are of the biggest step size. */
+	if ((this->flags & NC_BIGFIRST) && biggest_stepsize > 0) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+			uint vert_step = child_wid->GetVerticalStepSize(sizing);
+			if (vert_step == biggest_stepsize) {
+				num_changing_childs++;
+			}
+		}
+	}
+
 	/* Second loop: Allocate the additional vertical space over the resizing children, starting with the biggest resize steps. */
 	while (biggest_stepsize > 0) {
 		uint next_biggest_stepsize = 0;
@@ -1539,6 +1569,16 @@ void NWidgetVertical::AssignSizePosition(SizingType sizing, uint x, uint y, uint
 			next_biggest_stepsize = std::max(next_biggest_stepsize, vert_step);
 		}
 		biggest_stepsize = next_biggest_stepsize;
+
+		if (num_changing_childs == 0 && (flags & NC_BIGFIRST) && biggest_stepsize > 0) {
+			/* Second.5 loop: count how many children are of the updated biggest step size. */
+			for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+				uint vert_step = child_wid->GetVerticalStepSize(sizing);
+				if (vert_step == biggest_stepsize) {
+					num_changing_childs++;
+				}
+			}
+		}
 	}
 	assert(num_changing_childs == 0);
 

src/widget_type.h

@@ -458,9 +458,11 @@ public:
 /** Nested widget container flags, */
 enum NWidContainerFlags {
 	NCB_EQUALSIZE = 0, ///< Containers should keep all their (resizing) children equally large.
+	NCB_BIGFIRST  = 1, ///< Allocate space to biggest resize first.
 
 	NC_NONE = 0,                       ///< All flags cleared.
 	NC_EQUALSIZE = 1 << NCB_EQUALSIZE, ///< Value of the #NCB_EQUALSIZE flag.
+	NC_BIGFIRST  = 1 << NCB_BIGFIRST,  ///< Value of the #NCB_BIGFIRST flag.
 };
 DECLARE_ENUM_AS_BIT_SET(NWidContainerFlags)