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Composer items have a set of common properties you will find at the bottom of the Item Properties panel: Position and size, Rotation, Frame, Background, Item ID, Variables and Rendering (See figure_composer_common).
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QGIS now allows advanced rendering for Composer items just like vector and raster layers.
Each item inside the Composer can be moved and resized to create a perfect layout.For both operations the first step is to activate the Select/Move item tool and to click on the item; you can then move it using the mouse while holding the left button. If you need to constrain the movements to the horizontal or the vertical axis, just hold the Shift button on the keyboard while moving the mouse. If you need better precision, you can move a selected item using the Arrow keys on the keyboard; if the movement is too slow, you can speed up it by holding Shift.
A selected item will show squares on its boundaries; moving one of them with the mouse, will resize the item in the corresponding direction. While resizing, holding Shift will maintain the aspect ratio. Holding Alt will resize from the item center.
The correct position for an item can be obtained using the grid snapping or smart guides. Guides are set by clicking and dragging within the ruler area. To move a guide, click on the ruler, level with the guide and drag it to a new position. To delete a guide move it off the canvas. If you need to disable the snap on the fly, hold Ctrl while moving the mouse.
You can choose multiple items with the Select/Move item button. Just hold the Shift button and click on all the items you need. You can then resize/move this group like a single item.
Once you have found the correct position for an item, you can lock it by using the items on the toolbar or ticking the box next to the item in the Items panel. Locked items are not selectable on the canvas.
Locked items can be unlocked by selecting the item in the Items panel and unchecking the tickbox or you can use the icons on the toolbar.
To unselect an item, just click on it holding the Shift button.
Inside the Edit menu, you can find actions to select all the items, to clear all selections or to invert the current selection.
Raising or lowering the visual hierarchy for elements are inside the Raise selected items pull-down menu. Choose an element on the Print Composer canvas and select the matching functionality to raise or lower the selected element compared to the other elements. This order is shown in the Items panel. You can also raise or lower objects in the Items panel by clicking and dragging an object’s label in this list.
There are several alignment options available within the Align selected items pull-down menu (see figure_composer_common_align). To use an alignment function, you first select the elements then click on the matching alignment icon. All selected elements will then be aligned to their common bounding box. When moving items on the Composer canvas, alignment helper lines appear when borders, centers or corners are aligned.
The Variables lists all the variables available at the composer item’s level (which includes all global, project and composition’s variables). Map items also include Map settings variables that provide easy access to values like the map’s scale, extent, and so on.
In Variables, it’s also possible to manage item-level variables. Click the button to add a new custom variable. Likewise, select any custom item-level variable from the list and click the button to remove it.
More information on variables usage in the General Tools Variables section.