Support DPI change in candidate/infolist window (google#1481)

This is part of our ongoing effort to fully conform Per-Monitor DPI v2
protocol in Windows (google#831).

With this commit, both the candidate window and the infolist window
become fully aware of dynamic DPI changes. The indicator window and
icons managed by text input processor (TIP) DLLs remain unchanged.

The key implementation idea is to not rely on WM_DPICHANGED message [1].
It is really tempting to implement WM_DPICHANGED handler, but it turns
out to be redundant for our use cases. Consider the following two cases
explained in the WM_DPICHANGED message document [1].

 1. When the candidate/infolist window is moving into the monitor with a
    different DPI. In this case, win32::WindowManager should be aware of
    which monitor the candidate/infolist window will be displayed on,
    and can let the candidate/infolist window know the new DPI without
    relying on the WM_DPICHANGED message.

 2. When the DPI of the current monitor changes while the
    candidate/infolist window is visible. In this case, the target
    application window typically re-renders to adapt to the new DPI,
    which then triggers a fresh layout pass on our candidate/infolist
    window. As explained above, win32::WindowManager always checks the
    DPI of the target monitor without relying on the WM_DPICHANGED
    message.

Both cases arise because the candidate and infolist windows behave like
popups anchored to the cursor location in the target application
window; WM_DPICHANGED is primarily meaningful for top-level windows
that users can drag and move across the monitors.

Other than that, the implementation is rather straightforward: we just
need to make sure to keep propagating the DPI information to the text
renderer and to update the DPI-dependent resources when the DPI changes.

Closes google#1459.

 [1]: https://learn.microsoft.com/en-us/windows/win32/hidpi/wm-dpichanged

PiperOrigin-RevId: 906746593

Author: yukawa

src/bazel/win32/BUILD.bazel

@@ -97,6 +97,10 @@ mozc_win32_lib(
     name = "pathcch",
 )
 
+mozc_win32_lib(
+    name = "shcore",
+)
+
 mozc_win32_lib(
     name = "user32",
 )

src/renderer/win32/BUILD.bazel

@@ -107,6 +107,7 @@ mozc_cc_library(
     tags = MOZC_TAGS.WIN_ONLY,
     target_compatible_with = ["@platforms//os:windows"],
     deps = [
+        "//bazel/win32:shcore",
         "//bazel/win32:user32",
         "//protocol:renderer_cc_proto",
         "//renderer:renderer_style_handler",
@@ -122,6 +123,7 @@ mozc_cc_library(
     deps = [
         ":resource_h",
         ":text_renderer",
+        ":win32_dpi_util",
         "//base:const",
         "//base:coordinates",
         "//base/win32:wide_char",
@@ -251,6 +253,7 @@ mozc_cc_library(
         ":candidate_window",
         ":indicator_window",
         ":infolist_window",
+        ":win32_dpi_util",
         ":win32_renderer_util",
         "//base:coordinates",
         "//client:client_interface",

src/renderer/win32/candidate_window.cc

@@ -35,6 +35,7 @@
 #include <wil/resource.h>
 #include <windows.h>
 
+#include <cstdint>
 #include <memory>
 #include <sstream>
 #include <string>
@@ -57,9 +58,6 @@ namespace renderer {
 namespace win32 {
 namespace {
 
-// 96 DPI is the default DPI in Windows.
-constexpr int kDefaultDPI = 96;
-
 // layout size constants in pixel unit in the default DPI.
 constexpr int kIndicatorWidthInDefaultDPI = 4;
 
@@ -239,12 +237,19 @@ CandidateWindow::CandidateWindow()
       footer_logo_display_size_(0, 0),
       send_command_interface_(nullptr),
       table_layout_(std::make_unique<TableLayout>()),
-      text_renderer_(TextRenderer::Create()),
+      dpi_(::GetDpiForSystem()),
+      text_renderer_(TextRenderer::Create(dpi_)),
       indicator_width_(0),
       metrics_changed_(false),
       mouse_moving_(true) {
+  UpdateDpiDependentResources();
+}
+
+CandidateWindow::~CandidateWindow() = default;
+
+void CandidateWindow::UpdateDpiDependentResources() {
+  const double scale_factor = GetDPIScalingFactor(dpi_);
   double image_scale_factor = 1.0;
-  const double scale_factor = GetDPIScalingFactor();
   if (scale_factor < 1.125) {
     footer_logo_.reset(LoadBitmapFromResource(::GetModuleHandle(nullptr),
                                               IDB_FOOTER_LOGO_COLOR_100));
@@ -263,7 +268,7 @@ CandidateWindow::CandidateWindow()
     image_scale_factor = 2.0;
   }
 
-  // If DPI is not default value, re-calculate the size based on the DPI.
+  footer_logo_display_size_ = Size(0, 0);
   if (footer_logo_.is_valid()) {
     BITMAP bm = {};
     if (::GetObject(footer_logo_.get(), sizeof(bm), &bm)) {
@@ -276,13 +281,20 @@ CandidateWindow::CandidateWindow()
   indicator_width_ = kIndicatorWidthInDefaultDPI * scale_factor;
 }
 
-CandidateWindow::~CandidateWindow() {}
-
 LRESULT CandidateWindow::OnCreate(LPCREATESTRUCT create_struct) {
   EnableOrDisableWindowForWorkaround();
   return 0;
 }
 
+void CandidateWindow::UpdateDpi(uint32_t dpi) {
+  if (dpi == dpi_) {
+    return;
+  }
+  dpi_ = dpi;
+  UpdateDpiDependentResources();
+  text_renderer_->OnDpiChanged(dpi_);
+}
+
 void CandidateWindow::EnableOrDisableWindowForWorkaround() {
   // Disable the window if SPI_GETACTIVEWINDOWTRACKING is enabled.
   // See b/2317702 for details.
@@ -302,10 +314,6 @@ void CandidateWindow::OnDestroy() {
   ::PostQuitMessage(0);
 }
 
-void CandidateWindow::OnDpiChanged(UINT dpiX, UINT dpiY, RECT* rect) {
-  metrics_changed_ = true;
-}
-
 BOOL CandidateWindow::OnEraseBkgnd(HDC dc) {
   // We do not have to erase background
   // because all pixels in client area will be drawn in the DoPaint method.
@@ -839,7 +847,7 @@ void CandidateWindow::DrawSelectedRect(HDC dc) {
 
 void CandidateWindow::DrawInformationIcon(HDC dc) {
   DCHECK(table_layout_->IsLayoutFrozen()) << "Table layout is not frozen.";
-  const double scale_factor = GetDPIScalingFactor();
+  const double scale_factor = GetDPIScalingFactor(dpi_);
   for (size_t i = 0; i < candidate_window_->candidate_size(); ++i) {
     if (candidate_window_->candidate(i).has_information_id()) {
       CRect rect = ToCRect(table_layout_->GetRowRect(i));

src/renderer/win32/candidate_window.h

@@ -36,6 +36,7 @@
 #include <wil/resource.h>
 #include <windows.h>
 
+#include <cstdint>
 #include <memory>
 
 #include "base/const.h"
@@ -72,7 +73,6 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
   BEGIN_MSG_MAP(CandidateWindow)
   MESSAGE_HANDLER(WM_CREATE, OnCreate)
   MESSAGE_HANDLER(WM_DESTROY, OnDestroy)
-  MESSAGE_HANDLER(WM_DPICHANGED, OnDpiChanged)
   MESSAGE_HANDLER(WM_ERASEBKGND, OnEraseBkgnd)
   MESSAGE_HANDLER(WM_GETMINMAXINFO, OnGetMinMaxInfo)
   MESSAGE_HANDLER(WM_LBUTTONDOWN, OnLButtonDown)
@@ -89,7 +89,6 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
   ~CandidateWindow();
   LRESULT OnCreate(LPCREATESTRUCT create_struct);
   void OnDestroy();
-  void OnDpiChanged(UINT dpiX, UINT dpiY, RECT* rect);
   BOOL OnEraseBkgnd(HDC dc);
   void OnGetMinMaxInfo(MINMAXINFO* min_max_info);
   void OnLButtonDown(UINT nFlags, CPoint point);
@@ -101,6 +100,12 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
 
   void set_mouse_moving(bool moving);
 
+  // If |dpi| differs from the cached DPI, updates the cached DPI, refreshes
+  // DPI-dependent resources, and flags the text renderer for refresh on the
+  // next UpdateLayout. Idempotent — safe to call unconditionally before
+  // UpdateLayout.
+  void UpdateDpi(uint32_t dpi);
+
   void UpdateLayout(const commands::CandidateWindow& candidate_window);
   void SetSendCommandInterface(
       client::SendCommandInterface* send_command_interface);
@@ -123,6 +128,10 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
   void DrawBackground(HDC dc);
   void DrawFrame(HDC dc);
 
+  // Recomputes DPI-dependent cached resources (footer logo and indicator
+  // width) for the current |dpi_|.
+  void UpdateDpiDependentResources();
+
   // Handles candidate selection by mouse.
   void HandleMouseEvent(UINT nFlags, const CPoint& point,
                         bool close_candidatewindow);
@@ -142,13 +151,6 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
     OnDestroy();
     return 0;
   }
-  inline LRESULT OnDpiChanged(UINT msg_id, WPARAM wparam, LPARAM lparam,
-                              BOOL& handled) {
-    OnDpiChanged(static_cast<UINT>(LOWORD(wparam)),
-                 static_cast<UINT>(HIWORD(wparam)),
-                 reinterpret_cast<RECT*>(lparam));
-    return 0;
-  }
   inline LRESULT OnEraseBkgnd(UINT msg_id, WPARAM wparam, LPARAM lparam,
                               BOOL& handled) {
     return static_cast<LRESULT>(OnEraseBkgnd(reinterpret_cast<HDC>(wparam)));
@@ -198,6 +200,7 @@ class CandidateWindow : public ATL::CWindowImpl<CandidateWindow, ATL::CWindow,
   Size footer_logo_display_size_;
   client::SendCommandInterface* send_command_interface_;
   std::unique_ptr<TableLayout> table_layout_;
+  uint32_t dpi_;
   std::unique_ptr<TextRenderer> text_renderer_;
   int indicator_width_;
   bool metrics_changed_;

src/renderer/win32/indicator_window.cc

@@ -251,7 +251,7 @@ class IndicatorWindow::WindowImpl
 
   void LoadSprite(int mode) {
     BalloonImage::BalloonImageInfo info;
-    LOGFONT logfont = GetMessageBoxLogFont();
+    LOGFONT logfont = GetMessageBoxLogFont(::GetDpiForSystem());
     info.label_font = mozc::win32::WideToUtf8(logfont.lfFaceName);
 
     info.frame_color = RGBColor(1, 122, 204);

src/renderer/win32/infolist_window.cc

@@ -35,6 +35,7 @@
 #include <wil/resource.h>
 #include <windows.h>
 
+#include <cstdint>
 #include <string>
 
 #include "base/coordinates.h"
@@ -79,26 +80,32 @@ void FillSolidRect(HDC dc, const RECT* rect, COLORREF color) {
 InfolistWindow::InfolistWindow()
     : send_command_interface_(nullptr),
       candidate_window_(new commands::CandidateWindow),
-      text_renderer_(TextRenderer::Create()),
+      dpi_(::GetDpiForSystem()),
+      text_renderer_(TextRenderer::Create(dpi_)),
       style_(new RendererStyle),
       metrics_changed_(false),
       visible_(false) {
-  GetScaledRendererStyle(style_.get());
+  GetScaledRendererStyle(style_.get(), dpi_);
 }
 
 InfolistWindow::~InfolistWindow() {}
 
+void InfolistWindow::UpdateDpi(uint32_t dpi) {
+  if (dpi == dpi_) {
+    return;
+  }
+  dpi_ = dpi;
+  GetScaledRendererStyle(style_.get(), dpi_);
+  text_renderer_->OnDpiChanged(dpi_);
+}
+
 void InfolistWindow::OnDestroy() {
   // PostQuitMessage may stop the message loop even though other
   // windows are not closed. WindowManager should close these windows
   // before process termination.
   ::PostQuitMessage(0);
 }
 
-void InfolistWindow::OnDpiChanged(UINT dpiX, UINT dpiY, RECT* rect) {
-  metrics_changed_ = true;
-}
-
 BOOL InfolistWindow::OnEraseBkgnd(HDC dc) {
   // We do not have to erase background
   // because all pixels in client area will be drawn in the DoPaint method.

src/renderer/win32/infolist_window.h

@@ -35,6 +35,7 @@
 #include <atlwin.h>
 #include <windows.h>
 
+#include <cstdint>
 #include <memory>
 #include <string>
 
@@ -64,7 +65,6 @@ class InfolistWindow : public ATL::CWindowImpl<InfolistWindow, ATL::CWindow,
 
   BEGIN_MSG_MAP(InfolistWindow)
   MESSAGE_HANDLER(WM_DESTROY, OnDestroy)
-  MESSAGE_HANDLER(WM_DPICHANGED, OnDpiChanged)
   MESSAGE_HANDLER(WM_ERASEBKGND, OnEraseBkgnd)
   MESSAGE_HANDLER(WM_GETMINMAXINFO, OnGetMinMaxInfo)
   MESSAGE_HANDLER(WM_SETTINGCHANGE, OnSettingChange)
@@ -78,14 +78,19 @@ class InfolistWindow : public ATL::CWindowImpl<InfolistWindow, ATL::CWindow,
   InfolistWindow& operator=(const InfolistWindow&) = delete;
   ~InfolistWindow();
   void OnDestroy();
-  void OnDpiChanged(UINT dpiX, UINT dpiY, RECT* rect);
   BOOL OnEraseBkgnd(HDC dc);
   void OnGetMinMaxInfo(MINMAXINFO* min_max_info);
   void OnPaint(HDC dc);
   void OnPrintClient(HDC dc, UINT uFlags);
   void OnSettingChange(UINT uFlags, LPCTSTR lpszSection);
   void OnTimer(UINT_PTR nIDEvent);
 
+  // If |dpi| differs from the cached DPI, updates the cached DPI, re-scales
+  // |style_|, and flags the text renderer for refresh on the next
+  // UpdateLayout. Idempotent — safe to call unconditionally before
+  // UpdateLayout.
+  void UpdateDpi(uint32_t dpi);
+
   void UpdateLayout(const commands::CandidateWindow& candidates);
   void SetSendCommandInterface(
       client::SendCommandInterface* send_command_interface);
@@ -105,13 +110,6 @@ class InfolistWindow : public ATL::CWindowImpl<InfolistWindow, ATL::CWindow,
     OnDestroy();
     return 0;
   }
-  inline LRESULT OnDpiChanged(UINT msg_id, WPARAM wparam, LPARAM lparam,
-                              BOOL& handled) {
-    OnDpiChanged(static_cast<UINT>(LOWORD(wparam)),
-                 static_cast<UINT>(HIWORD(wparam)),
-                 reinterpret_cast<RECT*>(lparam));
-    return 0;
-  }
   inline LRESULT OnEraseBkgnd(UINT msg_id, WPARAM wparam, LPARAM lparam,
                               BOOL& handled) {
     return static_cast<LRESULT>(OnEraseBkgnd(reinterpret_cast<HDC>(wparam)));
@@ -145,6 +143,7 @@ class InfolistWindow : public ATL::CWindowImpl<InfolistWindow, ATL::CWindow,
 
   client::SendCommandInterface* send_command_interface_;
   std::unique_ptr<commands::CandidateWindow> candidate_window_;
+  uint32_t dpi_;
   std::unique_ptr<TextRenderer> text_renderer_;
   std::unique_ptr<renderer::RendererStyle> style_;
   bool metrics_changed_;