From 347773b673a1de57818d2f6041308a820e3a0828 Mon Sep 17 00:00:00 2001
From: Michael Ragazzon <michael.ragazzon@gmail.com>
Date: Thu, 31 Oct 2024 21:49:59 +0100
Subject: [PATCH] Add `CancelSelectBox()` method to `<select>` element, see
 #566

This reverts the value to the one set when the selection box was opened. This is particularly helpful for use cases where e.g. the "Escape" key should cancel the selection.

Added example usage to the demo sample.
---
 .../Core/Elements/ElementFormControlSelect.h   |  6 ++++--
 Samples/basic/demo/data/demo.rml               |  2 +-
 Samples/basic/demo/src/DemoEventListener.cpp   | 13 +++++++++++++
 .../Core/Elements/ElementFormControlSelect.cpp |  4 ++++
 Source/Core/Elements/WidgetDropDown.cpp        | 18 ++++++++++++++++++
 Source/Core/Elements/WidgetDropDown.h          |  4 ++++
 6 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/Include/RmlUi/Core/Elements/ElementFormControlSelect.h b/Include/RmlUi/Core/Elements/ElementFormControlSelect.h
index b5f55ba4b..ef26dde34 100644
--- a/Include/RmlUi/Core/Elements/ElementFormControlSelect.h
+++ b/Include/RmlUi/Core/Elements/ElementFormControlSelect.h
@@ -67,7 +67,7 @@ class RMLUICORE_API ElementFormControlSelect : public ElementFormControl {
 	int GetSelection() const;
 
 	/// Returns one of the select control's option elements.
-	/// @param[in] The index of the desired option.
+	/// @param[in] index The index of the desired option.
 	/// @return The option element or nullptr if the index was out of bounds.
 	Element* GetOption(int index);
 	/// Returns the number of options in the select control.
@@ -93,11 +93,13 @@ class RMLUICORE_API ElementFormControlSelect : public ElementFormControl {
 
 	/// Removes all options from the select control.
 	void RemoveAll();
-	
+
 	/// Show the selection box.
 	void ShowSelectBox();
 	/// Hide the selection box.
 	void HideSelectBox();
+	/// Revert to the value selected when the selection box was opened, then hide the box.
+	void CancelSelectBox();
 	/// Check whether the select box is opened or not.
 	bool IsSelectBoxVisible();
 
diff --git a/Samples/basic/demo/data/demo.rml b/Samples/basic/demo/data/demo.rml
index ef0ef6a80..83e19a41c 100644
--- a/Samples/basic/demo/data/demo.rml
+++ b/Samples/basic/demo/data/demo.rml
@@ -867,7 +867,7 @@ form .nav-auto, form input.checkbox, form input.radio
 		</div>
 		<h2>Subject</h2>
 		<div>
-			<select name="subject">
+			<select name="subject" onkeydown="cancel_selection_on_escape">
 				<option value="none" selected>Choose your subject</option>
 				<option value="feature">Feature request</option>
 				<option value="bug">Bug report</option>
diff --git a/Samples/basic/demo/src/DemoEventListener.cpp b/Samples/basic/demo/src/DemoEventListener.cpp
index 48871bfa0..d8a17f4ab 100644
--- a/Samples/basic/demo/src/DemoEventListener.cpp
+++ b/Samples/basic/demo/src/DemoEventListener.cpp
@@ -29,6 +29,7 @@
 #include "DemoWindow.h"
 #include <RmlUi/Core/Element.h>
 #include <RmlUi/Core/Elements/ElementFormControl.h>
+#include <RmlUi/Core/Elements/ElementFormControlSelect.h>
 #include <RmlUi_Backend.h>
 
 DemoEventListener::DemoEventListener(const Rml::String& value, Rml::Element* element, DemoWindow* demo_window) :
@@ -178,6 +179,18 @@ void DemoEventListener::ProcessEvent(Rml::Event& event)
 			demo_window->SetSandboxStylesheet(value);
 		}
 	}
+	else if (value == "cancel_selection_on_escape")
+	{
+		if (event.GetParameter("key_identifier", 0) == Input::KeyIdentifier ::KI_ESCAPE)
+		{
+			auto select_control = rmlui_dynamic_cast<Rml::ElementFormControlSelect*>(element);
+			if (select_control && select_control->IsSelectBoxVisible())
+			{
+				select_control->CancelSelectBox();
+				event.StopPropagation();
+			}
+		}
+	}
 }
 
 void DemoEventListener::OnDetach(Rml::Element* /*element*/)
diff --git a/Source/Core/Elements/ElementFormControlSelect.cpp b/Source/Core/Elements/ElementFormControlSelect.cpp
index c7353f1c6..3fd87bda4 100644
--- a/Source/Core/Elements/ElementFormControlSelect.cpp
+++ b/Source/Core/Elements/ElementFormControlSelect.cpp
@@ -119,6 +119,10 @@ void ElementFormControlSelect::HideSelectBox()
 {
 	widget->HideSelectBox();
 }
+void ElementFormControlSelect::CancelSelectBox()
+{
+	widget->CancelSelectBox();
+}
 
 bool ElementFormControlSelect::IsSelectBoxVisible()
 {
diff --git a/Source/Core/Elements/WidgetDropDown.cpp b/Source/Core/Elements/WidgetDropDown.cpp
index 167bc2f42..e2986cf87 100644
--- a/Source/Core/Elements/WidgetDropDown.cpp
+++ b/Source/Core/Elements/WidgetDropDown.cpp
@@ -634,6 +634,10 @@ void WidgetDropDown::ProcessEvent(Event& event)
 
 void WidgetDropDown::ShowSelectBox()
 {
+	if (box_visible)
+		return;
+
+	selected_value_on_box_open = parent_element->GetAttribute<String>("value", "");
 	selection_element->SetProperty(PropertyId::Visibility, Property(Style::Visibility::Visible));
 	selection_element->SetPseudoClass("checked", true);
 	value_element->SetPseudoClass("checked", true);
@@ -647,6 +651,9 @@ void WidgetDropDown::ShowSelectBox()
 
 void WidgetDropDown::HideSelectBox()
 {
+	if (!box_visible)
+		return;
+
 	selection_element->SetProperty(PropertyId::Visibility, Property(Style::Visibility::Hidden));
 	selection_element->RemoveProperty(PropertyId::Height);
 	selection_element->SetPseudoClass("checked", false);
@@ -657,6 +664,17 @@ void WidgetDropDown::HideSelectBox()
 	box_visible = false;
 }
 
+void WidgetDropDown::CancelSelectBox()
+{
+	if (!box_visible)
+		return;
+
+	if (parent_element->GetAttribute<String>("value", "") != selected_value_on_box_open)
+		parent_element->SetAttribute("value", selected_value_on_box_open);
+
+	HideSelectBox();
+}
+
 bool WidgetDropDown::IsSelectBoxVisible()
 {
 	return box_visible;
diff --git a/Source/Core/Elements/WidgetDropDown.h b/Source/Core/Elements/WidgetDropDown.h
index 300f666dc..48f5f2796 100644
--- a/Source/Core/Elements/WidgetDropDown.h
+++ b/Source/Core/Elements/WidgetDropDown.h
@@ -104,6 +104,8 @@ class WidgetDropDown : public EventListener {
 	void ShowSelectBox();
 	/// Hides the selection box.
 	void HideSelectBox();
+	/// Revert to the value selected when the selection box was opened, then hide the box.
+	void CancelSelectBox();
 	/// Check whether the select box is visible or not.
 	bool IsSelectBoxVisible();
 
@@ -119,6 +121,8 @@ class WidgetDropDown : public EventListener {
 	Element* selection_element;
 	Element* value_element;
 
+	String selected_value_on_box_open;
+
 	bool lock_selection = false;
 	bool selection_dirty = false;
 	bool value_rml_dirty = false;