Add a RegisterModified hook

This one has been a long time coming, I am still concerned this could
impact performance a lot. This hook does *not* trigger for capture
registers (0-9) or any other dynamic registers (that are not writable).

Fixes #859

doc/pages/hooks.asciidoc

@@ -175,6 +175,9 @@ name. Hooks with no description will always use an empty string.
     even with the `-with-hooks` option (see
     <<execeval#execute-keys-specific-switches,`:doc execeval execute-keys-specific-switches`>>).
 
+*RegisterModified* `register`::
+    Triggered after a register has been written to.
+
 *ModuleLoaded* `module`::
     Triggered after a module is evaluated by the first `require-module` call
 

src/hook_manager.hh

@@ -49,6 +49,7 @@ enum class Hook
     NormalKey,
     ModeChange,
     RawKey,
+    RegisterModified,
     WinClose,
     WinCreate,
     WinDisplay,
@@ -93,6 +94,7 @@ constexpr auto enum_desc(Meta::Type<Hook>)
         {Hook::NormalKey, "NormalKey"},
         {Hook::ModeChange, "ModeChange"},
         {Hook::RawKey, "RawKey"},
+        {Hook::RegisterModified, "RegisterModified"},
         {Hook::WinClose, "WinClose"},
         {Hook::WinCreate, "WinCreate"},
         {Hook::WinDisplay, "WinDisplay"},

src/main.cc

@@ -350,25 +350,28 @@ void register_registers()
 {
     RegisterManager& register_manager = RegisterManager::instance();
 
-    for (auto c : StringView{"abcdefghijklmnopqrstuvwxyz\"^@"})
-        register_manager.add_register(c, std::make_unique<StaticRegister>());
+    for (Codepoint c : StringView{"abcdefghijklmnopqrstuvwxyz\"^@"})
+        register_manager.add_register(c, std::make_unique<StaticRegister>(String{c}));
 
-    for (auto c : StringView{"/|:\\"})
-        register_manager.add_register(c, std::make_unique<HistoryRegister>());
+    for (Codepoint c : StringView{"/|:\\"})
+        register_manager.add_register(c, std::make_unique<HistoryRegister>(String{c}));
 
     using StringList = Vector<String, MemoryDomain::Registers>;
 
     register_manager.add_register('%', make_dyn_reg(
+        "%",
         [](const Context& context)
         { return StringList{{context.buffer().display_name()}}; }));
 
     register_manager.add_register('.', make_dyn_reg(
+        ".",
         [](const Context& context) {
             auto content = context.selections_content();
             return StringList{content.begin(), content.end()};
          }));
 
     register_manager.add_register('#', make_dyn_reg(
+        "#",
         [](const Context& context) {
             const size_t count = context.selections().size();
             StringList res;
@@ -381,6 +384,7 @@ void register_registers()
     for (size_t i = 0; i < 10; ++i)
     {
         register_manager.add_register('0'+i, make_dyn_reg(
+            String{Codepoint('0'+i)},
             [i](const Context& context) {
                 StringList result;
                 for (auto& sel : context.selections())

src/register_manager.cc

@@ -1,12 +1,59 @@
 #include "register_manager.hh"
 
 #include "assert.hh"
+#include "context.hh"
 #include "hash_map.hh"
 #include "string_utils.hh"
 
 namespace Kakoune
 {
 
+void StaticRegister::set(Context& context, ConstArrayView<String> values, bool)
+{
+    m_content.assign(values.begin(), values.end());
+    context.hooks().run_hook(Hook::RegisterModified, m_name, context);
+}
+
+ConstArrayView<String> StaticRegister::get(const Context&)
+{
+    if (m_content.empty())
+        return ConstArrayView<String>(String::ms_empty);
+    else
+        return ConstArrayView<String>(m_content);
+}
+
+const String& StaticRegister::get_main(const Context& context, size_t main_index)
+{
+    auto content = get(context);
+    return content[std::min(main_index, content.size() - 1)];
+}
+
+void HistoryRegister::set(Context& context, ConstArrayView<String> values, bool restoring)
+{
+    constexpr size_t size_limit = 100;
+
+    if (restoring)
+        return StaticRegister::set(context, values, true);
+
+    for (auto& entry : values)
+    {
+        m_content.erase(std::remove(m_content.begin(), m_content.end(), entry),
+                      m_content.end());
+        m_content.push_back(entry);
+    }
+
+    const size_t current_size = m_content.size();
+    if (current_size > size_limit)
+        m_content.erase(m_content.begin(), m_content.begin() + (current_size - size_limit));
+
+    context.hooks().run_hook(Hook::RegisterModified, m_name, context);
+}
+
+const String& HistoryRegister::get_main(const Context&, size_t)
+{
+    return m_content.empty() ? String::ms_empty : m_content.back();
+}
+
 static const HashMap<String, Codepoint> reg_names = {
     { "slash", '/' },
     { "dquote", '"' },

src/register_manager.hh

@@ -33,26 +33,14 @@ public:
 class StaticRegister : public Register
 {
 public:
-    void set(Context&, ConstArrayView<String> values, bool) override
-    {
-        m_content.assign(values.begin(), values.end());
-    }
-
-    ConstArrayView<String> get(const Context&) override
-    {
-        if (m_content.empty())
-            return ConstArrayView<String>(String::ms_empty);
-        else
-            return ConstArrayView<String>(m_content);
-    }
+    StaticRegister(String name) : m_name{std::move(name)} {}
 
-    const String& get_main(const Context& context, size_t main_index) override
-    {
-        auto content = get(context);
-        return content[std::min(main_index, content.size() - 1)];
-    }
+    void set(Context& context, ConstArrayView<String> values, bool) override;
+    ConstArrayView<String> get(const Context&) override;
+    const String& get_main(const Context& context, size_t main_index) override;
 
 protected:
+    String m_name;
     Vector<String, MemoryDomain::Registers> m_content;
 };
 
@@ -62,8 +50,8 @@ template<typename Getter, typename Setter>
 class DynamicRegister : public StaticRegister
 {
 public:
-    DynamicRegister(Getter getter, Setter setter)
-        : m_getter(std::move(getter)), m_setter(std::move(setter)) {}
+    DynamicRegister(String name, Getter getter, Setter setter)
+        : StaticRegister(std::move(name)), m_getter(std::move(getter)), m_setter(std::move(setter)) {}
 
     void set(Context& context, ConstArrayView<String> values, bool) override
     {
@@ -85,45 +73,26 @@ private:
 class HistoryRegister : public StaticRegister
 {
 public:
-    void set(Context& context, ConstArrayView<String> values, bool restoring) override
-    {
-        constexpr size_t size_limit = 100;
-
-        if (restoring)
-            return StaticRegister::set(context, values, true);
-
-        for (auto& entry : values)
-        {
-            m_content.erase(std::remove(m_content.begin(), m_content.end(), entry),
-                          m_content.end());
-            m_content.push_back(entry);
-        }
-
-        const size_t current_size = m_content.size();
-        if (current_size > size_limit)
-            m_content.erase(m_content.begin(), m_content.begin() + (current_size - size_limit));
-    }
+    using StaticRegister::StaticRegister;
 
-    const String& get_main(const Context&, size_t) override
-    {
-        return m_content.empty() ? String::ms_empty : m_content.back();
-    }
+    void set(Context& context, ConstArrayView<String> values, bool restoring) override;
+    const String& get_main(const Context&, size_t) override;
 };
 
 template<typename Func>
-std::unique_ptr<Register> make_dyn_reg(Func func)
+std::unique_ptr<Register> make_dyn_reg(String name, Func func)
 {
     auto setter = [](Context&, ConstArrayView<String>)
     {
         throw runtime_error("this register is not assignable");
     };
-    return std::make_unique<DynamicRegister<Func, decltype(setter)>>(std::move(func), setter);
+    return std::make_unique<DynamicRegister<Func, decltype(setter)>>(name, std::move(func), setter);
 }
 
 template<typename Getter, typename Setter>
-std::unique_ptr<Register> make_dyn_reg(Getter getter, Setter setter)
+std::unique_ptr<Register> make_dyn_reg(String name, Getter getter, Setter setter)
 {
-    return std::make_unique<DynamicRegister<Getter, Setter>>(std::move(getter), std::move(setter));
+    return std::make_unique<DynamicRegister<Getter, Setter>>(name, std::move(getter), std::move(setter));
 }
 
 class NullRegister : public Register