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Aspect Ratio

A layout wrapper that keeps one child at a fixed width to height ratio.

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Live C++Source and licences
#include <QApplication>
#include <QFile>
#include <QHBoxLayout>
#include <QLabel>
#include <QPainter>
#include <QStandardItemModel>
#include <QUrl>
#include <QVBoxLayout>
#include <array>
#ifdef SHADCN_GALLERY_MEDIA
#include <shadcn/media.hpp>
#endif
#include <shadcn/shadcn.hpp>

QWidget* example(QWidget* parent = nullptr) {
    using namespace shadcn;
    auto* canvas = new QWidget(parent);
    canvas->setAutoFillBackground(true);
    auto* outer = new QHBoxLayout(canvas);
    outer->setContentsMargins(32, 32, 32, 32);
    auto* host = new QWidget(canvas);
    auto* layout = new QVBoxLayout(host);
    layout->setContentsMargins(0, 0, 0, 0);
    layout->setSpacing(16);
    outer->addStretch();
    outer->addWidget(host, 0, Qt::AlignCenter);
    outer->addStretch();
    auto* aspect = new AspectRatio(16.0 / 9.0, host);
    aspect->setFixedWidth(320);
    auto* label = new QLabel("16 : 9", aspect);
    label->setAlignment(Qt::AlignCenter);
    label->setAutoFillBackground(true);
    auto palette = label->palette();
    palette.setColor(QPalette::Window, palette.color(QPalette::AlternateBase));
    label->setPalette(palette);
    aspect->setWidget(*label);
    layout->addWidget(aspect);
    return canvas;
}

Installation​

add_subdirectory(shadcn-cpp)
target_link_libraries(app PRIVATE shadcn::widgets)

Usage​

#include <shadcn/controls.hpp>
#include <QLabel>

shadcn::AspectRatio frame(16.0 / 9.0, parent);
auto* preview = new QLabel("Preview", &frame);
frame.setWidget(*preview);

API​

setRatio changes the ratio. setWidget installs the single child and heightForWidth lets Qt negotiate the size.

Variations​

Use a square ratio for avatars or a wide ratio for media previews.

Keyboard and accessibility​

Qt supplies native focus, keyboard interaction and accessible object roles. Give the component a visible label or an accessible name when its text alone does not explain the action.

Ownership​

The parent widget owns the component. Child widgets created through a component layout follow Qt parent ownership. References returned by helper methods are borrowed.