De-emphasize PluginManager::getObjects<Type>()

... by additionally keeping local (currently non-owning) pools per
"interesting" type.

Current situation:
  - The global object pool does not scale well for looking up
    objects, as iteration plus qobject_cast typically iterates
    over all pooled objects.
  - User code that can use typed results from the object
    pool need to have access to the full type definition anyway,
    i.e.  depend on the plugin of the target class anyway.

The patch here solves the scaling problem is to have local
type-specific pools to which objects register in their
constructors and deregister in their destructors.

This patch here does *not* change the ownership model of the
pooled objects, however, it opens the possibility to change
the ownership model per type (e.g. by not putting things into
the global pool at all anymore and make the local pool 'owning')
and the intent is to handle that in later patchs.

Even without the follow-up patches this here is a performance
improvement for the cases that access the local pools instead
the global one, i.e. "practically all".

Change-Id: Ib11a42df2c4ecf5e1155534730083a520dd1995b
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

4 files changed, 34 insertions, 9 deletions

diff --git a/src/plugins/texteditor/snippets/snippetprovider.cpp b/src/plugins/texteditor/snippets/snippetprovider.cpp
index 3791996d12f..13e95152323 100644
--- a/src/plugins/texteditor/snippets/snippetprovider.cpp
+++ b/src/plugins/texteditor/snippets/snippetprovider.cpp
@@ -27,8 +27,33 @@
 
 #include "texteditorplugin.h"
 
+#include <utils/algorithm.h>
+
 using namespace TextEditor;
 
+static QList<SnippetProvider *> g_snippetProviders;
+
+const QList<SnippetProvider *> SnippetProvider::snippetProviders()
+{
+    return g_snippetProviders;
+}
+
+SnippetProvider *SnippetProvider::snippetProviderForGroupId(const QString &groupId)
+{
+    return Utils::findOrDefault(g_snippetProviders,
+                                Utils::equal(&SnippetProvider::groupId, groupId));
+}
+
+SnippetProvider::SnippetProvider()
+{
+    g_snippetProviders.append(this);
+}
+
+SnippetProvider::~SnippetProvider()
+{
+    g_snippetProviders.removeOne(this);
+}
+
 /*!
     \group Snippets
     \title Snippets for Editors
diff --git a/src/plugins/texteditor/snippets/snippetprovider.h b/src/plugins/texteditor/snippets/snippetprovider.h
index 0bb0b0682cd..5c343df1823 100644
--- a/src/plugins/texteditor/snippets/snippetprovider.h
+++ b/src/plugins/texteditor/snippets/snippetprovider.h
@@ -41,6 +41,9 @@ class TEXTEDITOR_EXPORT SnippetProvider : public QObject
 public:
     using EditorDecorator = std::function<void(TextEditorWidget *)>;
 
+    static const QList<SnippetProvider *> snippetProviders();
+    static SnippetProvider *snippetProviderForGroupId(const QString &groupId);
+
     static void registerGroup(const QString &groupId, const QString &displayName,
                               EditorDecorator editorDecorator = EditorDecorator());
 
@@ -51,7 +54,8 @@ public:
     void decorateEditor(TextEditorWidget *editor) const;
 
 private:
-    SnippetProvider() = default;
+    SnippetProvider();
+    ~SnippetProvider() override;
 
     QString m_groupId;
     QString m_displayName;
diff --git a/src/plugins/texteditor/snippets/snippetscollection.cpp b/src/plugins/texteditor/snippets/snippetscollection.cpp
index 4aabbf2fd20..20c9615d5a6 100644
--- a/src/plugins/texteditor/snippets/snippetscollection.cpp
+++ b/src/plugins/texteditor/snippets/snippetscollection.cpp
@@ -409,9 +409,7 @@ int SnippetsCollection::groupIndex(const QString &groupId) const
 
 void SnippetsCollection::identifyGroups()
 {
-    const QList<SnippetProvider *> &providers =
-        ExtensionSystem::PluginManager::getObjects<SnippetProvider>();
-    foreach (SnippetProvider *provider, providers) {
+    for (SnippetProvider *provider : SnippetProvider::snippetProviders()) {
         const int groupIndex = m_groupIndexById.size();
         m_groupIndexById.insert(provider->groupId(), groupIndex);
         m_snippets.resize(groupIndex + 1);
diff --git a/src/plugins/texteditor/snippets/snippetssettingspage.cpp b/src/plugins/texteditor/snippets/snippetssettingspage.cpp
index 85b88d4eb4a..96a81d27f0e 100644
--- a/src/plugins/texteditor/snippets/snippetssettingspage.cpp
+++ b/src/plugins/texteditor/snippets/snippetssettingspage.cpp
@@ -328,9 +328,8 @@ void SnippetsSettingsPagePrivate::configureUi(QWidget *w)
 {
     m_ui.setupUi(w);
 
-    const QList<SnippetProvider *> &providers =
-        ExtensionSystem::PluginManager::getObjects<SnippetProvider>();
-    foreach (SnippetProvider *provider, providers) {
+    const QList<SnippetProvider *> &providers = SnippetProvider::snippetProviders();
+    for (SnippetProvider *provider : providers) {
         m_ui.groupCombo->addItem(provider->displayName(), provider->groupId());
         SnippetEditorWidget *snippetEditor = new SnippetEditorWidget(w);
         provider->decorateEditor(snippetEditor);
@@ -537,8 +536,7 @@ void SnippetsSettingsPagePrivate::setSnippetContent()
 
 void SnippetsSettingsPagePrivate::decorateEditors(const TextEditor::FontSettings &fontSettings)
 {
-    const QList<SnippetProvider *> &providers =
-        ExtensionSystem::PluginManager::getObjects<SnippetProvider>();
+    const QList<SnippetProvider *> &providers = SnippetProvider::snippetProviders();
     for (int i = 0; i < m_ui.groupCombo->count(); ++i) {
         SnippetEditorWidget *snippetEditor = editorAt(i);
         snippetEditor->textDocument()->setFontSettings(fontSettings);