Using C++Builder to list all available VCL styles in a ComboBox and apply a selected style using the ComboBoxChange event

Back in June a developer asked a C++Builder question on StackOverflow. The question was “How can I list all the available VCL styles in a combo box and in the ComboBoxChange event, apply that style in C++ Builder?” I answered the question and gave the example code.

One of my favorite RTL features for the VCL and FMX frameworks is the ability to customize the look and feel of your applications using Styles. The first step is to create a C++Builder VCL project and select a few of the VCL Styles in the Project | Options | Application | Appearance settings. The C++Builder 10.4 Sydney DocWiki explains that “the VCL Styles architecture has been significantly extended to support High-DPI graphics and 4K monitors. In 10.4 Sydney all graphical elements are automatically scaled for the proper resolution of the monitor the element is displayed on. This means that the scaling depends on the DPI resolution of the target computer or the current monitor, in case of multi-monitor systems.”

The C++ Application User Interface

For the application user interface I have a TButton (has code to populate the ComboBox with selected application styles) and a TComboBox (to display and allow selection of a style).

The C++ code

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
#include <Vcl.Themes.hpp>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
	// populate the ComboBox with VCL styles that are selected
	//    in Project | Options | Application | Appearance
	ComboBox1->Items->BeginUpdate();
    try
    {
		ComboBox1->Items->Clear();

		DynamicArray<String> styleNames = Vcl::Themes::TStyleManager::StyleNames;

        for(int i = 0; i < styleNames.Length; ++i)
        {
            String styleName = styleNames[i];
			ComboBox1->Items->Add(styleName);
        }
    }
    __finally
    {
		ComboBox1->Items->EndUpdate();
	}
}
//---------------------------------------------------------------------------
void __fastcall TForm1::ComboBox1Change(TObject *Sender)
{
	// set the style for the selected combobox item

	Vcl::Themes::TStyleManager::TrySetStyle(ComboBox1->Items->Strings[ComboBox1->ItemIndex],false);
}
//---------------------------------------------------------------------------

The Application in Action

TComboBox populated with VCL styles selected
Application Style Changed by TComboBox selection

References

VCL Styles Overview

Project Options Application Appearance

VCL Styles Support for High-DPI Graphics

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.

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