Calendar - Days selection with C++ binding.

It's possible to disable date selection and to select a date from your program, and that's what we'll see on this example.

The first part consists of including the headers. In this case we are only working with the Elementary C++ binding and thus we need only to include him.

#include <Elementary.hh>

If necessary the C and/or the C++ headers should be include here as well.

Now we need to actually start the code and set the elm_policy, which defines for a given policy group/identifier a new policy's value, respectively. In this example the only policy we need to set a value for is ELM_POLICY_QUIT, possibles values for it are:

elm_main (int argc, char *argv[])
struct tm selected_time;
time_t current_time;

As you can see, the policy we chose was to quit when the last win is hidden as opose to examples with the C bindings where we perpetually set it to quit when last win was closed. This changed was necessary because in C++ binding as the elm mainloop stop running all object are destroyed, references are unreferenced and events are stopped at ELM_MAIN().

See also
For more details consult elm_policy_set

Next step is creating an elementary window, in this example we use the C++ binding method with the elm_win_util_standard_add that is a elm_win_legacy function, better explained below. And then we set the autohide state for it.

elm_win_util_standard_add (const char *name, const char *tittle) Adds a window object with standard setup. Parameters:

This creates a window but also puts in a standard background with elm_bg_add(), as well as setting the window title to title. The window type created is of type ELM_WIN_BASIC, with the NULL as the parent widget. Returns the created object or NULL on failure.

The autohide works similarly to autodel, automatically handling "delete,request" signals when set to true, with the difference that it will hide the window, instead of destroying it.

It is specially designed to work together with ELM_POLICY_QUIT_LAST_WINDOW_HIDDEN which allows exiting Elementary's main loop when all the windows are hidden.

win.title_set("Calendar Day Selection Example");

autodel and autohide are not mutually exclusive. The window will be destructed if both autodel and autohide is set to EINA_TRUE or true.

In this example we'll need to use a elm::box to layout the two calendars that'll be created. A box arranges objects in a linear fashion, governed by a layout function that defines the details of this arrangement. The box will use an internal function to set the layout to a single row, vertical by default.

Now let's create the box with the C++ binding method, passing our window object as parent.

::elm::box bx(efl::eo::parent = win);

The function size_hint_weight_set for C++ bindings originated from C bindings function evas_object_size_hint_weight_set, that is EFL Evas type function. With this function we set the hints for an object's weight. The parameters are:

This is not a size enforcement in any way, it's just a hint that should be used whenever appropriate. This is a hint on how a container object should resize a given child within its area.

Containers may adhere to the simpler logic of just expanding the child object's dimensions to fit its own (see the EVAS_HINT_EXPAND helper weight macro in the EFL Evas Documentation) or the complete one of taking each child's weight hint as real weights to how much of its size to allocate for them in each axis. A container is supposed to, after normalizing the weights of its children (with weight hints), distribute the space it has to layout them by those factors – most weighted children get larger in this process than the least ones.

bx.size_hint_weight_set(EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);

Default weight hint values are 0.0, for both axis.

Now we add the box as a resize-object to win informing that when the size of the win changes so should the box's size. Remember always to set the box visibility to true.

Now let's create the calendar with the C++ binding method, passing our window object as parent. The function size_hint_weight_set works with calendar the same way as with box, for more, search above.

The function size_hint_align_set for C++ bindings originated from C bindings function evas_object_size_hint_align_set, that is EFL Evas type function. With this function we set the hints for an object's alignment. The parameters are:

These are hints on how to align an object inside the boundaries of a container/manager. Accepted values are in the 0.0 to 1.0 range, with the special value EVAS_HINT_FILL used to specify "justify" or "fill" by some users. In this case, maximum size hints should be enforced with higher priority, if they are set. Also, any padding hint set on objects should add up to the alignment space on the final scene composition.

For the horizontal component, 0.0 means to the left, 1.0 means to the right. Analogously, for the vertical component, 0.0 to the top, 1.0 means to the bottom.

This is not a size enforcement in any way, it's just a hint that should be used whenever appropriate.

Default alignment hint values are 0.5, for both axis.

If isn't required that users could select a day on calendar, only interacting going through months, disabling days selection could be a good idea to avoid confusion. For that:

When using the elm box the packing method of the subobj - calendar in this case - should be defined. There are four possible methods:

In this and most examples we use pack_end by choice and practicality. In this part of the code we also make calendar visible.

Also, regarding days selection, you could be interested to set a date to be highlighted on calendar from your code, maybe when a specific event happens or after calendar creation. As time output is in seconds, we define the number of seconds contained within a day as a constant:

#define SECS_DAY 86400

As with the first calendar, we'll also construct cal2, set it's hint_weight and hint_align, make cal2 visible and choose the packing method.

::elm::calendar cal2(efl::eo::parent = win);
cal2.size_hint_weight_set(EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);

Now let's select two days from current day:

current_time = time(NULL) +2 * SECS_DAY;
localtime_r(&current_time, &selected_time);

Finally we just have to make window visible and then start the elm mainloop, starting to handle events and drawing operations.

Our example will look like this:


See the full source code here.