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Codechange: make Window destruction not rely on undefined behavior.
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@frosch123
frosch123 committed May 12, 2021
1 parent f96f113 commit f6d5c01
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Showing 2 changed files with 63 additions and 140 deletions.
136 changes: 24 additions & 112 deletions src/window.cpp
View file
Expand Up @@ -53,10 +53,8 @@ static Point _drag_delta; ///< delta between mouse cursor and upper left corner
static Window *_mouseover_last_w = nullptr; ///< Window of the last OnMouseOver event.
static Window *_last_scroll_window = nullptr; ///< Window of the last scroll event.

/** List of windows opened at the screen sorted from the front. */
Window *_z_front_window = nullptr;
/** List of windows opened at the screen sorted from the back. */
Window *_z_back_window = nullptr;
/** List of windows opened at the screen sorted from the front to back. */
WindowList _z_windows;

/** If false, highlight is white, otherwise the by the widget defined colour. */
bool _window_highlight_colour = false;
Expand Down Expand Up @@ -1109,16 +1107,7 @@ Window::~Window()
free(this->nested_array); // Contents is released through deletion of #nested_root.
delete this->nested_root;

/*
* Make fairly sure that this is written, and not "optimized" away.
* The delete operator is overwritten to not delete it; the deletion
* happens at a later moment in time after the window has been
* removed from the list of windows to prevent issues with items
* being removed during the iteration as not one but more windows
* may be removed by a single call to ~Window by means of the
* DeleteChildWindows function.
*/
const_cast<volatile WindowClass &>(this->window_class) = WC_INVALID;
*this->z_position = nullptr;
}

/**
Expand Down Expand Up @@ -1231,7 +1220,7 @@ void ChangeWindowOwner(Owner old_owner, Owner new_owner)
}
}

static void BringWindowToFront(Window *w);
static void BringWindowToFront(Window *w, bool dirty = true);

/**
* Find a window and make it the relative top-window on the screen.
Expand Down Expand Up @@ -1351,90 +1340,23 @@ static uint GetWindowZPriority(WindowClass wc)
}
}

/**
* Adds a window to the z-ordering, according to its z-priority.
* @param w Window to add
*/
static void AddWindowToZOrdering(Window *w)
{
assert(w->z_front == nullptr && w->z_back == nullptr);

if (_z_front_window == nullptr) {
/* It's the only window. */
_z_front_window = _z_back_window = w;
w->z_front = w->z_back = nullptr;
} else {
/* Search down the z-ordering for its location. */
Window *v = _z_front_window;
uint last_z_priority = UINT_MAX;
(void)last_z_priority; // Unused without asserts
while (v != nullptr && (v->window_class == WC_INVALID || GetWindowZPriority(v->window_class) > GetWindowZPriority(w->window_class))) {
if (v->window_class != WC_INVALID) {
/* Sanity check z-ordering, while we're at it. */
assert(last_z_priority >= GetWindowZPriority(v->window_class));
last_z_priority = GetWindowZPriority(v->window_class);
}

v = v->z_back;
}

if (v == nullptr) {
/* It's the new back window. */
w->z_front = _z_back_window;
w->z_back = nullptr;
_z_back_window->z_back = w;
_z_back_window = w;
} else if (v == _z_front_window) {
/* It's the new front window. */
w->z_front = nullptr;
w->z_back = _z_front_window;
_z_front_window->z_front = w;
_z_front_window = w;
} else {
/* It's somewhere else in the z-ordering. */
w->z_front = v->z_front;
w->z_back = v;
v->z_front->z_back = w;
v->z_front = w;
}
}
}


/**
* Removes a window from the z-ordering.
* @param w Window to remove
*/
static void RemoveWindowFromZOrdering(Window *w)
{
if (w->z_front == nullptr) {
assert(_z_front_window == w);
_z_front_window = w->z_back;
} else {
w->z_front->z_back = w->z_back;
}

if (w->z_back == nullptr) {
assert(_z_back_window == w);
_z_back_window = w->z_front;
} else {
w->z_back->z_front = w->z_front;
}

w->z_front = w->z_back = nullptr;
}

/**
* On clicking on a window, make it the frontmost window of all windows with an equal
* or lower z-priority. The window is marked dirty for a repaint
* @param w window that is put into the relative foreground
* @param dirty whether to mark the window dirty
*/
static void BringWindowToFront(Window *w)
static void BringWindowToFront(Window *w, bool dirty)
{
RemoveWindowFromZOrdering(w);
AddWindowToZOrdering(w);
auto priority = GetWindowZPriority(w->window_class);
WindowList::iterator dest = _z_windows.begin();
while (dest != _z_windows.end() && (*dest == nullptr || GetWindowZPriority((*dest)->window_class) <= priority)) ++dest;

w->SetDirty();
if (dest != w->z_position) {
_z_windows.splice(dest, _z_windows, w->z_position);
}

if (dirty) w->SetDirty();
}

/**
Expand Down Expand Up @@ -1476,7 +1398,7 @@ void Window::InitializeData(WindowNumber window_number)
if (!EditBoxInGlobalFocus() || this->nested_root->GetWidgetOfType(WWT_EDITBOX) != nullptr) SetFocusedWindow(this);

/* Insert the window into the correct location in the z-ordering. */
AddWindowToZOrdering(this);
BringWindowToFront(this, false);
}

/**
Expand Down Expand Up @@ -1848,6 +1770,7 @@ void Window::InitNested(WindowNumber window_number)
*/
Window::Window(WindowDesc *desc) : window_desc(desc), mouse_capture_widget(-1)
{
this->z_position = _z_windows.insert(_z_windows.end(), this);
}

/**
Expand Down Expand Up @@ -1875,8 +1798,6 @@ void InitWindowSystem()
{
IConsoleClose();

_z_back_window = nullptr;
_z_front_window = nullptr;
_focused_window = nullptr;
_mouseover_last_w = nullptr;
_last_scroll_window = nullptr;
Expand All @@ -1898,14 +1819,7 @@ void UnInitWindowSystem()

for (Window *w : Window::Iterate()) delete w;

for (Window *w = _z_front_window; w != nullptr; /* nothing */) {
Window *to_del = w;
w = w->z_back;
free(to_del);
}

_z_front_window = nullptr;
_z_back_window = nullptr;
_z_windows.clear();
}

/**
Expand Down Expand Up @@ -3068,15 +2982,13 @@ void InputLoop()

CheckSoftLimit();

/* Do the actual free of the deleted windows. */
for (Window *v = _z_front_window; v != nullptr; /* nothing */) {
Window *w = v;
v = v->z_back;

if (w->window_class != WC_INVALID) continue;

RemoveWindowFromZOrdering(w);
free(w);
/* Remove dead entries from the window list */
for (auto it = _z_windows.begin(); it != _z_windows.end(); ) {
if (*it == nullptr) {
it = _z_windows.erase(it);
} else {
++it;
}
}

if (_input_events_this_tick != 0) {
Expand Down
67 changes: 39 additions & 28 deletions src/window_gui.h
View file
Expand Up @@ -10,6 +10,8 @@
#ifndef WINDOW_GUI_H
#define WINDOW_GUI_H

#include <list>

#include "vehicle_type.h"
#include "viewport_type.h"
#include "company_type.h"
Expand Down Expand Up @@ -143,8 +145,8 @@ void DrawFrameRect(int left, int top, int right, int bottom, Colours colour, Fra
void DrawCaption(const Rect &r, Colours colour, Owner owner, TextColour text_colour, StringID str, StringAlignment align);

/* window.cpp */
extern Window *_z_front_window;
extern Window *_z_back_window;
using WindowList = std::list<Window *>;
extern WindowList _z_windows;
extern Window *_focused_window;


Expand Down Expand Up @@ -293,19 +295,7 @@ struct Window : ZeroedMemoryAllocator {
* to destruct them all at the same time too, which is kinda hard.
* @param size the amount of space not to allocate
*/
inline void *operator new[](size_t size)
{
NOT_REACHED();
}

/**
* Helper allocation function to disallow something.
* Don't free the window directly; it corrupts the linked list when iterating
* @param ptr the pointer not to free
*/
inline void operator delete(void *ptr)
{
}
inline void *operator new[](size_t size) = delete;

WindowDesc *window_desc; ///< Window description
WindowFlags flags; ///< Window flags
Expand Down Expand Up @@ -336,8 +326,7 @@ struct Window : ZeroedMemoryAllocator {
int mouse_capture_widget; ///< Widgetindex of current mouse capture widget (e.g. dragged scrollbar). -1 if no widget has mouse capture.

Window *parent; ///< Parent window.
Window *z_front; ///< The window in front of us in z-order.
Window *z_back; ///< The window behind us in z-order.
WindowList::iterator z_position;

template <class NWID>
inline const NWID *GetWidget(uint widnum) const;
Expand Down Expand Up @@ -813,32 +802,45 @@ struct Window : ZeroedMemoryAllocator {

/**
* Iterator to iterate all valid Windows
* @tparam Tfront Wether we iterate from front
* @tparam TtoBack whether we iterate towards the back.
*/
template <bool Tfront>
template <bool TtoBack>
struct WindowIterator {
typedef Window *value_type;
typedef value_type *pointer;
typedef value_type &reference;
typedef size_t difference_type;
typedef std::forward_iterator_tag iterator_category;

explicit WindowIterator(const Window *start) : w(const_cast<Window *>(start))
explicit WindowIterator(WindowList::iterator start) : it(start)
{
this->Validate();
}
explicit WindowIterator(const Window *w) : it(w->z_position) {}

bool operator==(const WindowIterator &other) const { return this->w == other.w; }
bool operator==(const WindowIterator &other) const { return this->it == other.it; }
bool operator!=(const WindowIterator &other) const { return !(*this == other); }
Window * operator*() const { return this->w; }
Window * operator*() const { return *this->it; }
WindowIterator & operator++() { this->Next(); this->Validate(); return *this; }

bool IsEnd() const { return this->w == nullptr; }
bool IsEnd() const { return this->it == _z_windows.end(); }

private:
Window *w;
void Validate() { while (this->w != nullptr && this->w->window_class == WC_INVALID) this->Next(); }
void Next() { if (this->w != nullptr) this->w = Tfront ? this->w->z_back : this->w->z_front; }
WindowList::iterator it;
void Validate()
{
while (!this->IsEnd() && *this->it == nullptr) this->Next();
}
void Next()
{
if constexpr (!TtoBack) {
++this->it;
} else if (this->it == _z_windows.begin()) {
this->it = _z_windows.end();
} else {
--this->it;
}
}
};
using IteratorToFront = WindowIterator<false>; //!< Iterate in Z order towards front.
using IteratorToBack = WindowIterator<true>; //!< Iterate in Z order towards back.
Expand All @@ -850,8 +852,17 @@ struct Window : ZeroedMemoryAllocator {
template <bool Tfront>
struct AllWindows {
AllWindows() {}
WindowIterator<Tfront> begin() { return WindowIterator<Tfront>(Tfront ? _z_front_window : _z_back_window); }
WindowIterator<Tfront> end() { return WindowIterator<Tfront>(nullptr); }
WindowIterator<Tfront> begin()
{
if constexpr (Tfront) {
auto back = _z_windows.end();
if (back != _z_windows.begin()) --back;
return WindowIterator<Tfront>(back);
} else {
return WindowIterator<Tfront>(_z_windows.begin());
}
}
WindowIterator<Tfront> end() { return WindowIterator<Tfront>(_z_windows.end()); }
};
using Iterate = AllWindows<false>; //!< Iterate all windows in whatever order is easiest.
using IterateFromBack = AllWindows<false>; //!< Iterate all windows in Z order from back to front.
Expand Down

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