To be honest, I've never met a designer who, on their own, gave a moment's consideration to designing the latest corporate template so it could handle all the presentations that the client already has. It just doesn't seem to be part of today's design esthetic to consider anything but the today and the future.
That's not how your client sees it. For rapid production of new presentations, the last thing they want it to have to re-invent their presentations every time the brand is overhauled. It's far more efficient to reuse slides that already tell the story. But to reuse those slides easily, the designer must be an integral part of the process.
Legacy Slides - Everything You Know is Wrong
Despite the hyperbole of my headline borrowed from Firesign Theater (look it up, youngsters!), most designers create presentation template incorrectly, for the purpose of importing of legacy slides. Almost universal infractions include deleting or renaming the default slide layouts, and deleting or adding placeholders on whatever default slide layouts are left. Less common methods that designers use to wreck templates include deleting all placeholders on the master slide, and deleting all default layouts, then trying to replace them
To understand why these actions could cause problems, we need to understand the PowerPoint file structure. All new blank PowerPoint files contain the following:
1 Master Slide (in Slide Master view, the larger slide at the top). The parent to all the layouts, to which the slide layouts are children.
11 default slide layouts, which inherit the formatting set in the master slide. These 11 comprise:
Title Slide, for the presentation title.
Title and Content, for the bulk of the presentation content.
Section Header, to divide the deck into relevant sections.
Two Content, with 2 content areas.
Comparison, similar to Two Content, but each content area also has a corresponding heading placeholder.
Title Only, displaying only a Title field, with the rest of the slide blank.
Blank, with not even a Title field.
Content with Caption, a little-used layout the includes a Title, Text and Content placeholder.
Picture with Caption, similar to Content with Caption, but with a Picture placeholder replacing the Content one.
Title and Vertical Text This layout is intended for Asian language use and is only displayed as a choice if your operating system has an Asian language set up.
Vertical Title and Text Similar to the previous layout, only available on computers with Asian language input enabled in the operating system.
Each of these layouts has a specific layout type, set in XML and not alterable in the program interface. You can create the correct placeholder types by generating a new, blank PowerPoint file. Each of these layouts contains placeholders for the date and slide number, plus a footer field. All but 1 have a title placeholder.
Here's the second line of a default layout. In this example, obj is the XML type for a Title and Content layout:
If a slide layout has been created by the user from the Insert Layout command, that layout will not have a type. Instead, the second line of the XML will include userDrawn="1"
If you have deleted a default slide layout, you can restore it by creating a new blank presentation, then copying and pasting the layout under the slide master of the deck to be repaired. You can also restore a default layout by running this VBA:
Dim oSl As Slide
Count% = ActivePresentation.Slides.Count
Set oSl = ActivePresentation.Slides.Add(Index:=(Count% + 1), Layout:=ppLayoutObject)
Set oSl = Nothing
The example above restores a deleted Title and Content layout. Just change ppLayoutObject to the type you need from this list:
Title and Content
Content with Caption
Picture with Caption
Title and Vertical Text
Vertical Title and Text
Legacy Slides - What Actually Works
PowerPoint, like most programs, is bonehead stupid. When you paste in old slides, and you want them to map to your new slide layouts, they must meet all of these criteria:
The slide layout name must be the same.
The slide layout type (as set in XML) must be the same. If you copy an existing Title Slide layout, it will retain the layout type. But if you delete all Title Slide layouts, then realize you made a mistake, you are hosed. It should be possible to recreate a layout with it's XML type using VBA, I'll post that when I code it.
The number of placeholders must be the same. When there is a different number of placeholders on the slide being pasted, PowerPoint goes mental and will reassign content randomly.
The types of placeholders must be the same. If a user is pasting a Title and Content slide, PowerPoint is looking for:
1 Title, 1 Content, 1 Date, 1 Footer and 1 Page Number placeholder. No more, no less.
For corresponding placeholders in the old and new layouts, the idx number must match. Title placeholders don't have idx numbers, because there is only one of them on a slide at a time. The idx numbers tell PowerPoint which placeholder should receive information from a particular placeholder in the old layout. This allows you to have several of the same type of placeholder on a layout and still have PowerPoint map content correctly among them.
An additional wrinkle can appear if an embedded image is included, perhaps for a logo. Then the XML will include a line line this:
rId numbers are used by the _rels file that corresponds with the layout to tell PowerPoint where to find the logo. If the rId number is wrong, PowerPoint will show an empty box with the text The picture could not be displayed. Of course, you could just replace the image if you see this error during file construction.
Static pictures, graphics, text boxes and shapes placed on the layout make no difference to layout mapping. Add them, remove them, they won't stop PowerPoint finding the correct layout.
If a pasted slide does not meet all of the above criteria, PowerPoint imports the slide layout from the old deck, prepending it's name with 1_, if it's the first time it's importing that layout. Very quickly, the client's deck is polluted with multiple spurious slide layouts. When face with choices like Title and Content, 1_Title and Content, 2_Title and Content, 3_Title and Content, the user will simply give up trying to decide which one to use. Branding goes down the drain.
Here are the recommendations that Microsoft should have published with the release of PowerPoint 2007: All new PowerPoint templates should include all default slide layouts and placeholders. That would have saved so much grief!
Please note, I am not suggesting that you restrict your design to only these layouts and placeholders. As long as you have the default layouts with the default placeholders, the rest of the master slide can be filled with all kinds of special-purpose layouts with any number of placeholders. Just remember, what ever you create today must be supported in the future. Restraint in slide layout numbers is best for your client's users. Too many layouts and they just don't know which one to pick!
To extend this to today, all new templates you create for a client should include the slide layouts and placeholders of all previous templates they have commissioned. Sometimes it's feasible to segregate these using different slide masters, one for each previous template they have used. Each slide master includes exactly the layouts and placeholders used in a previous version. Then in the receiving template, the user is instructed to paste immediately after a slide based on an earlier version. This method can reduce the user's pain of having to follow your shiny new template.
We have years of expertise in this area and can either assess your template for legacy slide compatibility or create a template or theme for you that will work seamlessly with your old files. We're here to help! Contact me at firstname.lastname@example.org.