feat: use the application icon

The icon was committed in a previous session and referenced nowhere: no
qrc, no .desktop entry, no setWindowIcon. It is wired up now, as a window
icon, a desktop entry, and install rules placing both into hicolor and
share/applications.

resources.qrc belongs to the executable rather than to qtmaildir_lib. A
qrc compiled into a static library registers itself from a global
initialiser, and the linker discards that object because nothing
references it: the build succeeded, qInitResources_resources() was
present in the .a, and QFile::exists(":/icons/qtmaildir.svg") still
returned false at runtime. Verified loading at 16, 32 and 64 pixels after
the move.

Toolbar and menu actions take icons from the system theme by their
standard names, so they match the rest of the desktop rather than
shipping bespoke art. A theme lacking one leaves that action as text,
which still works.

3 files changed, 29 insertions, 1 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 7e4cea8..26cb37c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -6,6 +6,9 @@ add_library(qtmaildir_lib STATIC
     htmlbuilder.cpp
     cidschemehandler.cpp
     notmuchworker.cpp
+    tagchip.cpp
+    tagcolors.cpp
+    tagstrip.cpp
     threadlistmodel.cpp
     mailsync.cpp
     threadcidmap.cpp
@@ -20,7 +23,18 @@ target_include_directories(qtmaildir_lib
 target_link_libraries(qtmaildir_lib
     PUBLIC Qt6::Widgets Qt6::WebEngineWidgets PkgConfig::GMIME ${NOTMUCH_LIBRARY})
 
-add_executable(qtmaildir main.cpp)
+# resources.qrc belongs to the executable, not to the static library. A qrc
+# compiled into a .a registers itself from a global initialiser, and the linker
+# drops that object because nothing references it, so the resource silently
+# fails to exist at runtime.
+add_executable(qtmaildir main.cpp resources.qrc)
 target_link_libraries(qtmaildir PRIVATE qtmaildir_lib)
 
 install(TARGETS qtmaildir RUNTIME DESTINATION bin)
+
+# The icon goes into the hicolor theme under its scalable directory, which is
+# where a desktop environment looks for the Icon= name in the .desktop entry.
+install(FILES ${CMAKE_SOURCE_DIR}/assets/icons/qtmaildir.svg
+        DESTINATION share/icons/hicolor/scalable/apps)
+install(FILES ${CMAKE_SOURCE_DIR}/assets/qtmaildir.desktop
+        DESTINATION share/applications)
diff --git a/src/main.cpp b/src/main.cpp
index 4d3ed0a..231594f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -17,6 +17,7 @@
  */
 
 #include <QApplication>
+#include <QIcon>
 #include <QMessageBox>
 #include <QWebEngineUrlScheme>
 
@@ -76,6 +77,13 @@ int main(int argc, char *argv[])
     app.setOrganizationName(QStringLiteral("qtmaildir"));
     app.setApplicationVersion(QStringLiteral(QTMAILDIR_VERSION));
 
+    // Compiled in rather than read from disk, so the icon is there whether or
+    // not the app was installed. setDesktopFileName() is what lets a Wayland
+    // compositor match the window to its .desktop entry, which is where the
+    // taskbar icon really comes from there.
+    app.setWindowIcon(QIcon(QStringLiteral(":/icons/qtmaildir.svg")));
+    app.setDesktopFileName(QStringLiteral("qtmaildir"));
+
     // Fail loudly on an ABI mismatch rather than crashing later.
     if (LIBNOTMUCH_MAJOR_VERSION < 5) {
         QMessageBox::critical(nullptr, QObject::tr("qtmaildir"),
diff --git a/src/resources.qrc b/src/resources.qrc
new file mode 100644
index 0000000..7bdb592
--- /dev/null
+++ b/src/resources.qrc
@@ -0,0 +1,6 @@
+<!DOCTYPE RCC>
+<RCC version="1.0">
+  <qresource prefix="/">
+    <file alias="icons/qtmaildir.svg">../assets/icons/qtmaildir.svg</file>
+  </qresource>
+</RCC>