After many years of maintaining and developing the pre-Fedora 18 installer, the installer development team determined that a rewrite of the installer was necessary for a myriad of reasons, including the following:
The previous installer had an aging (around 13 years old) infrastructure that was difficult and time-consuming to maintain and improve, constraining new feature development. One current install team developer refers to the old infrastructure as "an incredible mess."
The performance of the old installer left a lot to be desired. Long-term tasks could not be performed in the background. This required long wait times and pauses throughout the installation experience. For example, as CPU and time-intensive tasks were processed, the UI would freeze for several moments until a given processing task completed.
The previous UI was not very responsive. This manifested in various ways, including a failure of the UI screens to redraw when the display was changed between a TTY and back to the UI.
The text-only version of the installer interface was a completely separate codebase, which increased the maintenance burden of the installer. This also increased the amount of work needed to implement new features as they would need to be written twice, once for each codebase.
The previous codebase was not written in a modular fashion. This caused issues where similar functionality in different modes (for example, GUI vs kickstart) used different logic and resulted in inconsistencies for users.
The automated kickstart mode of the installer was separate and incompatible with the UI modes of the installer. A separate utility, system-config-kickstart, was created solely to provide a UI for creating kickstarts since the existing UI could not be used for this purpose without a completed install.
The live media method of installation used a different codepath than the installer than the DVD method, causing maintenance and development difficulties and resulting in an inconsistent and at times buggy user experience.
The old installer's interface had a 'point of no return' past which any changes you'd made to your storage configuration could destroy data on your disk(s) and you couldn't go back to change it. Since the UI followed a linear path, this exact inflection point occurred close to the middle of the screen flow and required a rather discouraging pop-up dialog to explain the impact.
In previous versions of Fedora, the installer's interface followed a wizard design pattern , consisting of multiple linear screens with occasional nested modal pop-up dialogs. (See diagram below) While nothing is inherently problematic with wizards as a design pattern, the sheer number of screens required by the installer made it unwieldy. You could end up several screens into the process and need to go back and change something on an earlier screen, requiring a lot of clicking and screen flipping to go back and return to where you left off. Multiple modal nested dialog windows also made it confusing at times to interact with certain screens, in particular the partitioning-related screens.