Tab hover card: page snapshot thumbnails

CMakeLists.txt

@@ -88,6 +88,8 @@ set(BRO_SRCS
     src/radix_icons.mm
     src/tab_description_fetcher.cc
     src/tab_description_fetcher.h
+    src/tab_thumbnail_fetcher.cc
+    src/tab_thumbnail_fetcher.h
 )
 
 set(BRO_HELPER_SRCS
@@ -194,6 +196,7 @@ target_link_libraries(${EXECUTABLE_NAME}
     libcef_dll_wrapper
     ${CEF_STANDARD_LIBS}
     "-framework QuartzCore"
+    "-framework ImageIO"
     "-F${sparkle_SOURCE_DIR}"
     "-framework Sparkle"
 )

src/bro_handler.cc

@@ -44,7 +44,9 @@ std::string EscapeHTML(const std::string& text) {
 }  // namespace
 
 BroHandler::BroHandler(bool is_alloy_style)
-    : is_alloy_style_(is_alloy_style), tab_description_fetcher_(this) {
+    : is_alloy_style_(is_alloy_style),
+      tab_description_fetcher_(this),
+      tab_thumbnail_fetcher_(this) {
   DCHECK(!g_instance);
   g_instance = this;
 }
@@ -77,6 +79,12 @@ void BroHandler::SetActiveBrowser(int browser_id) {
     return;
   }
 
+  // Snapshot the outgoing tab for its hover-card thumbnail while the
+  // compositor surface still holds the on-screen frame; the capture resolves
+  // asynchronously and tolerates the WasHidden that follows.
+  tab_thumbnail_fetcher_.Fetch(
+      browser_registry_.GetById(browser_registry_.active_id()));
+
   CefRefPtr<CefBrowser> browser = browser_registry_.SetActive(browser_id);
   if (browser) {
     OnActiveTabChanged(browser_id);
@@ -202,6 +210,17 @@ void BroHandler::FetchTabDescription(int browser_id) {
   tab_description_fetcher_.Fetch(browser);
 }
 
+void BroHandler::FetchTabThumbnail(int browser_id) {
+  if (!CefCurrentlyOn(TID_UI)) {
+    CefPostTask(TID_UI, base::BindOnce(&BroHandler::FetchTabThumbnail, this,
+                                       browser_id));
+    return;
+  }
+
+  CefRefPtr<CefBrowser> browser = browser_registry_.GetById(browser_id);
+  tab_thumbnail_fetcher_.Fetch(browser);
+}
+
 void BroHandler::OnDevToolsMethodResult(CefRefPtr<CefBrowser> browser,
                                         int message_id,
                                         bool success,
@@ -210,6 +229,8 @@ void BroHandler::OnDevToolsMethodResult(CefRefPtr<CefBrowser> browser,
   CEF_REQUIRE_UI_THREAD();
   tab_description_fetcher_.HandleMethodResult(browser, message_id, success,
                                               result, result_size);
+  tab_thumbnail_fetcher_.HandleMethodResult(browser, message_id, success,
+                                            result, result_size);
 }
 
 void BroHandler::ApplyEmulationToBrowser(CefRefPtr<CefBrowser> browser,
@@ -405,6 +426,7 @@ void BroHandler::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
   browser_registry_.Remove(browser);
   mobile_tab_ids_.erase(browser_id);
   tab_description_fetcher_.OnBrowserClosed(browser_id);
+  tab_thumbnail_fetcher_.OnBrowserClosed(browser_id);
 
   // Notify UI about tab closure
   OnTabClosed(browser_id);

src/bro_handler.h

@@ -10,6 +10,7 @@
 #include "include/cef_devtools_message_observer.h"
 #include "include/cef_download_handler.h"
 #include "tab_description_fetcher.h"
+#include "tab_thumbnail_fetcher.h"
 
 #include <set>
 
@@ -117,6 +118,12 @@ class BroHandler : public CefClient,
   // assumes the DevTools result callback fires.
   void FetchTabDescription(int browser_id);
 
+  // Asynchronously captures a snapshot of the tab's page via the DevTools
+  // protocol; the result arrives through OnTabThumbnailAvailable.
+  // Best-effort: silently does nothing if the browser is gone, and never
+  // assumes the DevTools result callback fires.
+  void FetchTabThumbnail(int browser_id);
+
   // CefClient methods:
   CefRefPtr<CefDisplayHandler> GetDisplayHandler() override { return this; }
   CefRefPtr<CefFindHandler> GetFindHandler() override { return this; }
@@ -254,6 +261,9 @@ class BroHandler : public CefClient,
   // DevTools CDP round trip that backs FetchTabDescription.
   TabDescriptionFetcher tab_description_fetcher_;
 
+  // DevTools CDP round trip that backs FetchTabThumbnail.
+  TabThumbnailFetcher tab_thumbnail_fetcher_;
+
   // True while CloseAllBrowsers is tearing everything down (window close /
   // app quit). Individual tab closes are handled by detaching the tab's view
   // in DoClose; the whole-window close goes through the OS close path.

src/bro_mac.mm

@@ -4,6 +4,7 @@
 // found in the LICENSE file.
 
 #import <Cocoa/Cocoa.h>
+#import <ImageIO/ImageIO.h>
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
@@ -2674,6 +2675,51 @@ void OnTabDescriptionAvailable(int browser_id, const std::string& description) {
   });
 }
 
+void OnTabThumbnailAvailable(int browser_id, const std::string& jpeg_base64) {
+  // Convert before dispatching (see UpdateURL).
+  NSString* base64Str =
+      [NSString stringWithUTF8String:jpeg_base64.c_str()] ?: @"";
+  // Decode and downscale off-main (the favicon loader's pattern); only
+  // delivery hops to main. The 512px cap bounds decoded memory to ~1MB per
+  // tab while staying above 2x of the hover card's drawn size.
+  dispatch_async(dispatch_get_global_queue(QOS_CLASS_UTILITY, 0), ^{
+    NSImage* image = nil;
+    NSData* data = [[NSData alloc]
+        initWithBase64EncodedString:base64Str
+                            options:
+                                NSDataBase64DecodingIgnoreUnknownCharacters];
+    if (data.length > 0) {
+      CGImageSourceRef source =
+          CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
+      if (source) {
+        NSDictionary* opts = @{
+          (__bridge NSString*)kCGImageSourceCreateThumbnailFromImageAlways :
+              @YES,
+          (__bridge NSString*)kCGImageSourceThumbnailMaxPixelSize : @512,
+        };
+        CGImageRef thumb = CGImageSourceCreateThumbnailAtIndex(
+            source, 0, (__bridge CFDictionaryRef)opts);
+        if (thumb) {
+          image = [[NSImage alloc]
+              initWithCGImage:thumb
+                         size:NSMakeSize(CGImageGetWidth(thumb),
+                                         CGImageGetHeight(thumb))];
+          CGImageRelease(thumb);
+        }
+        CFRelease(source);
+      }
+    }
+    if (!image) {
+      return;
+    }
+    dispatch_async(dispatch_get_main_queue(), ^{
+      if (g_tab_bar) {
+        [g_tab_bar updateTabThumbnail:browser_id image:image];
+      }
+    });
+  });
+}
+
 void OnTabURLChanged(int browser_id, const std::string& url) {
   // Convert before dispatching (see UpdateURL).
   NSString* urlStr = [NSString stringWithUTF8String:url.c_str()] ?: @"";
@@ -2717,6 +2763,18 @@ void OnTabLoadingChanged(int browser_id, bool is_loading) {
     if (g_tab_bar) {
       [g_tab_bar updateTabLoading:browser_id loading:is_loading];
     }
+    // Refresh the hover-card thumbnail when a visible tab finishes loading;
+    // hidden tabs get theirs at switch-away time instead (their compositor
+    // may not produce frames).
+    if (!is_loading && ![g_blank_tab_ids containsObject:@(browser_id)]) {
+      BroHandler* handler = BroHandler::GetInstance();
+      BOOL visible = handler &&
+                     (browser_id == handler->GetActiveBrowserId() ||
+                      (SplitActive() && browser_id == g_split_browser_id));
+      if (visible) {
+        handler->FetchTabThumbnail(browser_id);
+      }
+    }
   });
 }
 

src/bro_mac_internal.h

@@ -85,6 +85,11 @@ static const NSTimeInterval kViewportAnimDuration = 0.28;
 static const NSTimeInterval kHoverCardDelay = 1.0;
 static const NSTimeInterval kHoverCardHideGrace = 0.3;
 static const CGFloat kHoverCardButtonSize = 24.0;
+// The card's page-snapshot band: inset from the card edges (its corner
+// radius stays concentric with the glass surface) and the fixed 16:10
+// crop it is aspect-filled into.
+static const CGFloat kHoverCardThumbnailInset = 6.0;
+static const CGFloat kHoverCardThumbnailAspect = 10.0 / 16.0;
 // Hover/press icon feedback: the whole button scales about its center,
 // animated by the shared 0.15s ease-out layer actions. Kept subtle so the
 // chrome stays calm; skipped entirely under Reduce Motion.
@@ -325,6 +330,10 @@ extern NSTextField* BroHoverCardLabel(NSFont* font, CGFloat whiteAlpha);
 // nil until fetched (empty string = fetched, page has none). Cleared whenever
 // tabURL changes.
 @property (nonatomic, copy) NSString* pageDescription;
+// Page snapshot captured via DevTools for the hover card; nil until a
+// capture lands. Cleared whenever tabURL changes; refreshed at switch-away,
+// on load-complete while visible, and on hover.
+@property (nonatomic, strong) NSImage* pageThumbnail;
 @property (nonatomic, weak) id target;
 @property (nonatomic, assign) SEL selectAction;
 @property (nonatomic, assign) SEL closeAction;
@@ -382,6 +391,7 @@ extern NSTextField* BroHoverCardLabel(NSFont* font, CGFloat whiteAlpha);
 - (void)tabFocusEnded:(BroTabView*)tab;
 - (void)hideHoverCard;
 - (void)updateTabDescription:(int)browserId description:(NSString*)desc;
+- (void)updateTabThumbnail:(int)browserId image:(NSImage*)image;
 // Toggles the tab's pinned state, moving it across the pinned/unpinned
 // boundary (pinned pills are a strict prefix of the strip).
 - (void)togglePinForTab:(BroTabView*)tab;

src/bro_tabstrip.mm

@@ -611,8 +611,9 @@ - (void)setFaviconURL:(NSString*)urlString {
 - (void)setTabURL:(NSString*)url {
   NSString* newURL = [url copy] ?: @"";
   if (![_tabURL isEqualToString:newURL]) {
-    // The cached meta description belongs to the old page.
+    // The cached meta description and snapshot belong to the old page.
     _pageDescription = nil;
+    _pageThumbnail = nil;
   }
   _tabURL = newURL;
   NSString* display = BroURLIsBlank(_tabURL)
@@ -1167,15 +1168,18 @@ @interface BroTabHoverCard : NSView
 // The tab bar owning the hover lifecycle; told when the mouse enters/leaves
 // the card so the grace-period hide can be canceled and re-armed.
 @property (nonatomic, weak) BroTabBar* hoverDelegate;
-// Populates the labels and resizes self to fit; caller positions the frame.
+// Populates the labels and snapshot band and resizes self to fit; caller
+// positions the frame.
 - (void)setTitle:(NSString*)title
              url:(NSString*)url
      pageDescription:(NSString*)desc
+       thumbnail:(NSImage*)thumbnail
            width:(CGFloat)width;
 @end
 
 @implementation BroTabHoverCard {
   NSView* contentHost_;
+  NSView* thumbnailView_;
   BroShimmerTextView* titleLabel_;
   NSTextField* urlLabel_;
   NSTextField* descriptionLabel_;
@@ -1218,6 +1222,21 @@ - (instancetype)initWithFrame:(NSRect)frame {
     descriptionLabel_ = BroHoverCardLabel(BroUIFont(11.0), 0.75);
     descriptionLabel_.lineBreakMode = NSLineBreakByWordWrapping;
     descriptionLabel_.cell.wraps = YES;
+
+    // Page snapshot band; absent until a capture lands. A plain layer-backed
+    // view rather than an NSImageView: aspect-fill + masksToBounds center-
+    // crops captures whose aspect differs from the band's (e.g. the portrait
+    // mobile-emulation viewport).
+    thumbnailView_ = [[NSView alloc] initWithFrame:NSZeroRect];
+    thumbnailView_.wantsLayer = YES;
+    thumbnailView_.layer.masksToBounds = YES;
+    thumbnailView_.layer.contentsGravity = kCAGravityResizeAspectFill;
+    // Hairline to seat light page content on the glass.
+    thumbnailView_.layer.borderWidth = 1.0;
+    thumbnailView_.layer.borderColor =
+        [[NSColor labelColor] colorWithAlphaComponent:0.08].CGColor;
+    thumbnailView_.hidden = YES;
+    [contentHost_ addSubview:thumbnailView_];
     [contentHost_ addSubview:titleLabel_];
     [contentHost_ addSubview:urlLabel_];
     [contentHost_ addSubview:descriptionLabel_];
@@ -1270,6 +1289,7 @@ - (void)mouseExited:(NSEvent*)event {
 - (void)setTitle:(NSString*)title
              url:(NSString*)url
      pageDescription:(NSString*)desc
+       thumbnail:(NSImage*)thumbnail
            width:(CGFloat)width {
   const CGFloat padX = 12.0;
   const CGFloat padY = 10.0;
@@ -1280,6 +1300,11 @@ - (void)setTitle:(NSString*)title
   urlLabel_.stringValue = url ?: @"";
   descriptionLabel_.stringValue = desc ?: @"";
   descriptionLabel_.hidden = desc.length == 0;
+  thumbnailView_.hidden = thumbnail == nil;
+  thumbnailView_.layer.contents =
+      thumbnail
+          ? (id)[thumbnail CGImageForProposedRect:NULL context:nil hints:nil]
+          : nil;
   self.accessibilityLabel = title.length > 0
       ? [NSString stringWithFormat:@"Tab preview: %@", title]
       : @"Tab preview";
@@ -1301,12 +1326,22 @@ - (void)setTitle:(NSString*)title
 
   // Space between the text block and the action-button row beneath it.
   const CGFloat buttonRowGap = 8.0;
+  // Space between the snapshot band and the title beneath it.
+  const CGFloat thumbnailGap = 8.0;
+  CGFloat thumbnailWidth = width - kHoverCardThumbnailInset * 2;
+  CGFloat thumbnailHeight =
+      thumbnail ? round(thumbnailWidth * kHoverCardThumbnailAspect) : 0;
 
   CGFloat height = padY * 2 + titleHeight + rowGap + urlHeight +
                    buttonRowGap + kHoverCardButtonSize;
   if (descriptionHeight > 0) {
     height += rowGap + descriptionHeight;
   }
+  if (thumbnailHeight > 0) {
+    // The snapshot band swaps the top text padding for its tighter inset.
+    height +=
+        thumbnailHeight + thumbnailGap + kHoverCardThumbnailInset - padY;
+  }
 
   // Flipped-less (default) coords: title on top, buttons at the bottom. The
   // buttons overhang padX slightly so their icons (not their hover
@@ -1328,6 +1363,13 @@ - (void)setTitle:(NSString*)title
   urlLabel_.frame = NSMakeRect(padX, y, textWidth, urlHeight);
   y += urlHeight + rowGap;
   titleLabel_.frame = NSMakeRect(padX, y, textWidth, titleHeight);
+  if (thumbnailHeight > 0) {
+    y += titleHeight + thumbnailGap;
+    thumbnailView_.layer.cornerRadius = BroNestedCornerRadius(
+        self.layer.cornerRadius, kHoverCardThumbnailInset);
+    thumbnailView_.frame = NSMakeRect(kHoverCardThumbnailInset, y,
+                                      thumbnailWidth, thumbnailHeight);
+  }
 
   [self setFrameSize:NSMakeSize(width, height)];
 }
@@ -2457,22 +2499,36 @@ - (void)showHoverCardForTab:(BroTabView*)tab {
     [hoverCard_ setTitle:kBroBlankTabTitle
                      url:@"Ask anything…"
          pageDescription:nil
+               thumbnail:nil
                    width:width];
   } else {
     [hoverCard_ setTitle:[self hoverCardTitleForTab:tab]
                      url:BroDisplayHostForURL(tab.tabURL)
          pageDescription:tab.pageDescription
+               thumbnail:tab.pageThumbnail
                    width:width];
   }
   [self positionHoverCardForTab:tab animated:wasVisible];
   BroOverlayShow(hoverCard_);
 
   // Fetch the description on first hover per page; the card shows right away
   // with title + URL and fills in when (if) the result arrives.
-  if (tab.pageDescription == nil && !BroURLIsBlank(tab.tabURL)) {
+  if (!BroURLIsBlank(tab.tabURL)) {
     BroHandler* handler = BroHandler::GetInstance();
     if (handler) {
-      handler->FetchTabDescription(tab.browserId);
+      if (tab.pageDescription == nil) {
+        handler->FetchTabDescription(tab.browserId);
+      }
+      // Snapshot: refresh a visible tab (its compositor is live), or make a
+      // best-effort first capture for a background tab that has none — a
+      // hidden browser often still serves its last surface frame; if the
+      // capture never resolves, the card simply stays text-only.
+      BOOL visibleTab =
+          tab.browserId == _activeTabId ||
+          (SplitActive() && tab.browserId == g_split_browser_id);
+      if (visibleTab || tab.pageThumbnail == nil) {
+        handler->FetchTabThumbnail(tab.browserId);
+      }
     }
   }
 }
@@ -2512,6 +2568,32 @@ - (void)updateTabDescription:(int)browserId description:(NSString*)desc {
       [hoverCard_ setTitle:[self hoverCardTitleForTab:tab]
                        url:BroDisplayHostForURL(tab.tabURL)
            pageDescription:tab.pageDescription
+                 thumbnail:tab.pageThumbnail
+                     width:hoverCard_.frame.size.width];
+      [self positionHoverCardForTab:tab animated:YES];
+    }
+    break;
+  }
+}
+
+- (void)updateTabThumbnail:(int)browserId image:(NSImage*)image {
+  if (!image) {
+    return;
+  }
+  for (BroTabView* tab in _tabs) {
+    if (tab.browserId != browserId) {
+      continue;
+    }
+    tab.pageThumbnail = image;
+    // Live-fill the visible card (the frame re-spring animates the growth).
+    // A tab that went blank since the capture keeps its "New Tab" card
+    // instead of a stale page's snapshot.
+    if (hoverCardTabId_ == browserId && hoverCard_ && !hoverCard_.hidden &&
+        !BroURLIsBlank(tab.tabURL)) {
+      [hoverCard_ setTitle:[self hoverCardTitleForTab:tab]
+                       url:BroDisplayHostForURL(tab.tabURL)
+           pageDescription:tab.pageDescription
+                 thumbnail:tab.pageThumbnail
                      width:hoverCard_.frame.size.width];
       [self positionHoverCardForTab:tab animated:YES];
     }