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cc55c442a3
When merging two dives, if a divesite is chosen that doesn't have a GPS location, but another divesite has a GPS location, then the GPS location of the former is set to that of the latter. However, that was done outside of the undo system, so that it is not undone and the frontend is not made aware of the change. Fix this. To simplify things, move the code from the undo machinery to the core. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
185 lines
9.7 KiB
C++
185 lines
9.7 KiB
C++
// SPDX-License-Identifier: GPL-2.0
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// Note: this header file is used by the undo-machinery and should not be included elsewhere.
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#ifndef COMMAND_BASE_H
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#define COMMAND_BASE_H
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#include "core/divesite.h"
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#include "core/trip.h"
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#include "core/dive.h"
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#include <QUndoCommand>
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#include <QCoreApplication> // For Q_DECLARE_TR_FUNCTIONS
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#include <memory>
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// The classes derived from Command::Base represent units-of-work, which can be exectuted / undone
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// repeatedly. The command objects are collected in a linear list implemented in the QUndoStack class.
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// They contain the information that is necessary to either perform or undo the unit-of-work.
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// The usage is:
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// constructor: generate information that is needed for executing the unit-of-work
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// redo(): performs the unit-of-work and generates the information that is needed for undo()
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// undo(): undos the unit-of-work and regenerates the initial information needed in redo()
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// The needed information is mostly kept in pointers to dives and/or trips, which have to be added
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// or removed.
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// For this to work it is crucial that
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// 1) Pointers to dives and trips remain valid as long as referencing command-objects exist.
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// 2) The dive-table is not resorted, because dives are inserted at given indices.
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//
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// Thus, if a command deletes a dive or a trip, the actual object must not be deleted. Instead,
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// the command object removes pointers to the dive/trip object from the backend and takes ownership.
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// To reverse such a deletion, the object is re-injected into the backend and ownership is given up.
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// Once ownership of a dive is taken, any reference to it was removed from the backend. Thus,
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// subsequent redo()/undo() actions cannot access this object and integrity of the data is ensured.
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//
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// As an example, consider the following course of events: Dive 1 is renumbered and deleted, dive 2
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// is added and renumbered. The undo list looks like this (---> non-owning, ***> owning pointers,
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// ===> next item in list)
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//
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// Undo-List
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// +-----------------+ +---------------+ +------------+ +-----------------+
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// | Renumber dive 1 |====>| Delete dive 1 |====>| Add dive 2 |====>| Renumber dive 2 |
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// +------------------ +---------------+ +------------+ +-----------------+
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// | * | |
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// | +--------+ * | +--------+ |
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// +----->| Dive 1 |<****** +--->| Dive 2 |<------+
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// +--------+ +--------+
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// ^
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// +---------+ *
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// | Backend |****************
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// +---------+
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// Two points of note:
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// 1) Every dive is owned by either the backend or exactly one command object.
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// 2) All references to dive 1 are *before* the owner "delete dive 2", thus the pointer is always valid.
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// 3) References by the backend are *always* owning.
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//
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// The user undos the last two commands. The situation now looks like this:
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//
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//
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// Undo-List Redo-List
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// +-----------------+ +---------------+ +------------+ +-----------------+
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// | Renumber dive 1 |====>| Delete dive 1 | | Add dive 2 |<====| Renumber dive 2 |
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// +------------------ +---------------+ +------------+ +-----------------+
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// | * * |
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// | +--------+ * * +--------+ |
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// +----->| Dive 1 |<****** ****>| Dive 2 |<------+
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// +--------+ +--------+
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//
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// +---------+
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// | Backend |
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// +---------+
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// Again:
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// 1) Every dive is owned by either the backend (here none) or exactly one command object.
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// 2) All references to dive 1 are *before* the owner "delete dive 1", thus the pointer is always valid.
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// 3) All references to dive 2 are *after* the owner "add dive 2", thus the pointer is always valid.
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//
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// The user undos one more command:
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//
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// Undo-List Redo-List
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// +-----------------+ +---------------+ +------------+ +-----------------+
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// | Renumber dive 1 | | Delete dive 1 |<====| Add dive 2 |<====| Renumber dive 2 |
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// +------------------ +---------------+ +------------+ +-----------------+
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// | | * |
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// | +--------+ | * +--------+ |
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// +----->| Dive 1 |<-----+ ****>| Dive 2 |<------+
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// +--------+ +--------+
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// ^
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// * +---------+
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// ***************| Backend |
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// +---------+
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// Same points as above.
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// The user now adds a dive 3. The redo list will be deleted:
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//
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// Undo-List
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// +-----------------+ +------------+
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// | Renumber dive 1 |=============================================>| Add dive 3 |
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// +------------------ +------------+
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// | |
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// | +--------+ +--------+ |
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// +----->| Dive 1 | | Dive 3 |<---+
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// +--------+ +--------+
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// ^ ^
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// * +---------+ *
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// ***************| Backend |****************
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// +---------+
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// Note:
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// 1) Dive 2 was deleted with the "add dive 2" command, because that was the owner.
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// 2) Dive 1 was not deleted, because it is owned by the backend.
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//
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// To take ownership of dives/trips, std::unique_ptr<>s are used.
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// Expressed in C-terms: std::unique_ptr<T> is the same as T* with the following
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// twists:
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// 1) default-initialized to NULL.
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// 2) if it goes out of scope (local scope or containing object destroyed), it does:
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// if (ptr) free_function(ptr);
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// whereby free_function can be configured (defaults to delete ptr).
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// 3) assignment between two std::unique_ptr<T> compiles only if the source is reset (to NULL).
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// (hence the name - there's a *unique* owner).
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// While this sounds trivial, experience shows that this distinctly simplifies memory-management
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// (it's not necessary to manually delete all vector items in the destructur, etc).
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// Note that Qt's own implementation (QScoperPointer) is not up to the job, because it doesn't implement
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// move-semantics and Qt's containers are incompatible, owing to COW semantics.
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//
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// Usage:
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// std::unique_ptr<dive> dPtr; // Initialize to null-state: not owning any dive.
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// std::unique_ptr<dive> dPtr(dive); // Take ownership of dive (which is of type struct dive *).
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// // If dPtr goes out of scope, the dive will be freed with free_dive().
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// struct dive *d = dPtr.release(); // Give up ownership of dive. dPtr is reset to null.
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// struct dive *d = d.get(); // Get pointer dive, but don't release ownership.
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// dPtr.reset(dive2); // Delete currently owned dive with free_dive() and get ownership of dive2.
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// dPtr.reset(); // Delete currently owned dive and reset to null.
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// dPtr2 = dPtr1; // Fails to compile.
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// dPtr2 = std::move(dPtr1); // dPtr2 takes ownership, dPtr1 is reset to null.
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// std::unique_ptr<dive> fun();
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// dPtr1 = fun(); // Compiles. Simply put: the compiler knows that the result of fun() will
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// // be trashed and therefore can be moved-from.
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// std::vector<std::unique_ptr<dive>> v: // Define an empty vector of owning pointers.
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// v.emplace_back(dive); // Take ownership of dive and add at end of vector
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// // If the vector goes out of scope, all dives will be freed with free_dive().
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// v.clear(v); // Reset the vector to zero length. If the elements weren't release()d,
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// // the pointed-to dives are freed with free_dive()
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// Qt is making their containers a lot harder to integrate with std::vector
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template<typename T>
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QVector<T> stdToQt(const std::vector<T> &v)
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{
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#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
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return QVector<T>(v.begin(), v.end());
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#else
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return QVector<T>::fromStdVector(v);
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#endif
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}
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template<typename T>
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std::vector<T> qtToStd(const QVector<T> &v)
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{
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return std::vector<T>(v.begin(), v.end());
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}
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// We put everything in a namespace, so that we can shorten names without polluting the global namespace
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namespace Command {
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// This is the base class of all commands.
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// It defines the Qt-translation functions
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class Base : public QUndoCommand {
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Q_DECLARE_TR_FUNCTIONS(Command)
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public:
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// Check whether work is to be done.
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// TODO: replace by setObsolete (>Qt5.9)
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virtual bool workToBeDone() = 0;
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};
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// Put a command on the undoStack (and take ownership), but test whether there
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// is something to be done beforehand by calling the workToBeDone() function.
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// If nothing is to be done, the command will be deleted and false is returned.
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bool execute(Base *cmd);
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// helper function to create more meaningful undo/redo texts (and get the list
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// of those texts for the git storage commit message)
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QUndoStack *getUndoStack();
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QString diveNumberOrDate(struct dive *d);
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QString getListOfDives(const std::vector<dive *> &dives);
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QString getListOfDives(QVector<struct dive *> dives);
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} // namespace Command
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#endif // COMMAND_BASE_H
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