flutter_flutter/shell/platform/windows/win32_dpi_utils.cc
James Clarke d0d6a4c236
Refactor Win32FlutterWindow in preparation for UWP windowing implementation (#18878)
* Add flutter_windows_view and window_binding_handler

Switch input handling infra to FlutterWindowsView

win32_flutter_window implement WindowBindingHandler

Strip unneeded functionality from win32flutterwindow

Fulfill WindowBindingHandler interface in Win32FlutterWindow

Add implementations for missing input handling in Win32FlutterWindow

Cleanup dead code

Correctly hook up rendering again

Fix resizing

clang-format

Fix clipboard

Cleanup

Rename

Add comments

cleanup

* clang-format

* CR Feedback

* clang-format; gn format

* Fix licensing

* CR feedback

* CR feedback

* CR feedback

* Git rid of unnecessar :: prefixes

* Extract WindowBindingHandlerDelegate as an interface

* Missing file

* Extract physical window bounds as a struct

* CR Feedback

* CR feedback

* clang-format

Co-authored-by: Stuart Morgan <stuartmorgan@google.com>
2020-07-07 06:49:51 -07:00

130 lines
3.9 KiB
C++

#include "win32_dpi_utils.h"
namespace flutter {
namespace {
constexpr UINT kDefaultDpi = 96;
// This is the MDT_EFFECTIVE_DPI value from MONITOR_DPI_TYPE, an enum declared
// in ShellScalingApi.h. Replicating here to avoid importing the library
// directly.
constexpr UINT kEffectiveDpiMonitorType = 0;
template <typename T>
/// Retrieves a function |name| from a given |comBaseModule| into |outProc|.
/// Returns a bool indicating whether the function was found.
bool AssignProcAddress(HMODULE comBaseModule, const char* name, T*& outProc) {
outProc = reinterpret_cast<T*>(GetProcAddress(comBaseModule, name));
return *outProc != nullptr;
}
/// A helper class for abstracting various Windows DPI related functions across
/// Windows OS versions.
class Win32DpiHelper {
public:
Win32DpiHelper();
~Win32DpiHelper();
/// Returns the DPI for |hwnd|. Supports all DPI awareness modes, and is
/// backward compatible down to Windows Vista. If |hwnd| is nullptr, returns
/// the DPI for the primary monitor. If Per-Monitor DPI awareness is not
/// available, returns the system's DPI.
UINT GetDpiForWindow(HWND);
/// Returns the DPI of a given monitor. Defaults to 96 if the API is not
/// available.
UINT GetDpiForMonitor(HMONITOR);
private:
using GetDpiForWindow_ = UINT __stdcall(HWND);
using GetDpiForMonitor_ = HRESULT __stdcall(HMONITOR hmonitor,
UINT dpiType,
UINT* dpiX,
UINT* dpiY);
using EnableNonClientDpiScaling_ = BOOL __stdcall(HWND hwnd);
GetDpiForWindow_* get_dpi_for_window_ = nullptr;
GetDpiForMonitor_* get_dpi_for_monitor_ = nullptr;
EnableNonClientDpiScaling_* enable_non_client_dpi_scaling_ = nullptr;
HMODULE user32_module_ = nullptr;
HMODULE shlib_module_ = nullptr;
bool dpi_for_window_supported_ = false;
bool dpi_for_monitor_supported_ = false;
};
Win32DpiHelper::Win32DpiHelper() {
if ((user32_module_ = LoadLibraryA("User32.dll")) != nullptr) {
dpi_for_window_supported_ = (AssignProcAddress(
user32_module_, "GetDpiForWindow", get_dpi_for_window_));
}
if ((shlib_module_ = LoadLibraryA("Shcore.dll")) != nullptr) {
dpi_for_monitor_supported_ = AssignProcAddress(
shlib_module_, "GetDpiForMonitor", get_dpi_for_monitor_);
}
}
Win32DpiHelper::~Win32DpiHelper() {
if (user32_module_ != nullptr) {
FreeLibrary(user32_module_);
}
if (shlib_module_ != nullptr) {
FreeLibrary(shlib_module_);
}
}
UINT Win32DpiHelper::GetDpiForWindow(HWND hwnd) {
// GetDpiForWindow returns the DPI for any awareness mode. If not available,
// or no |hwnd| is provided, fallback to a per monitor, system, or default
// DPI.
if (dpi_for_window_supported_ && hwnd != nullptr) {
return get_dpi_for_window_(hwnd);
}
if (dpi_for_monitor_supported_) {
HMONITOR monitor = nullptr;
if (hwnd != nullptr) {
monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTOPRIMARY);
}
return GetDpiForMonitor(monitor);
}
HDC hdc = GetDC(hwnd);
UINT dpi = GetDeviceCaps(hdc, LOGPIXELSX);
ReleaseDC(hwnd, hdc);
return dpi;
}
UINT Win32DpiHelper::GetDpiForMonitor(HMONITOR monitor) {
if (dpi_for_monitor_supported_) {
if (monitor == nullptr) {
const POINT target_point = {0, 0};
monitor = MonitorFromPoint(target_point, MONITOR_DEFAULTTOPRIMARY);
}
UINT dpi_x = 0, dpi_y = 0;
HRESULT result =
get_dpi_for_monitor_(monitor, kEffectiveDpiMonitorType, &dpi_x, &dpi_y);
if (SUCCEEDED(result)) {
return dpi_x;
}
}
return kDefaultDpi;
} // namespace
Win32DpiHelper* GetHelper() {
static Win32DpiHelper* dpi_helper = new Win32DpiHelper();
return dpi_helper;
}
} // namespace
UINT GetDpiForHWND(HWND hwnd) {
return GetHelper()->GetDpiForWindow(hwnd);
}
UINT GetDpiForMonitor(HMONITOR monitor) {
return GetHelper()->GetDpiForMonitor(monitor);
}
} // namespace flutter