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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/dw-line-breaking.doc | 100 |
1 files changed, 76 insertions, 24 deletions
diff --git a/doc/dw-line-breaking.doc b/doc/dw-line-breaking.doc index 12e89829..8e520c62 100644 --- a/doc/dw-line-breaking.doc +++ b/doc/dw-line-breaking.doc @@ -167,10 +167,11 @@ word \f$i\f$. \f$h_i\f$ is the width of the hyphen, if the word \f$i\f$ is a part of the hyphenated word (except the last part); otherwise 0. -Let \f$l\f$ be the (ideal) width (length) of the line. Furthermore, -all words from \f$a\f$ to \f$b\f$ are added to the line. \f$a\f$ is -fixed: we do not modify the previous lines anymore; but our task is to -find a suitable \f$b\f$. +Let \f$l\f$ be the (ideal) width (length) of the line, which is +e. at the top given by the browser window width. Furthermore, all words +from \f$a\f$ to \f$b\f$ are added to the line. \f$a\f$ is fixed: we do +not modify the previous lines anymore; but our task is to find a +suitable \f$b\f$. We define: @@ -333,17 +334,16 @@ be easily extended. <h3>High Priority</h3> -<ul> -<li>There seem to be problems when breaking words containing hyphens -already. Example: "Abtei-Stadt", which is divided into "Abtei-" and -"Stadt", resulting possibly in "Abtei--[new line]Stadt". See also -below under "Low Priority", on how to deal with hyphens and dashes.</li> -</ul> +<b>Bugs in hyphenation:</b> There seem to be problems when breaking +words containing hyphens already. Example: "Abtei-Stadt", which is +divided into "Abtei-" and "Stadt", resulting possibly in +"Abtei-<span></span>-[new line]Stadt". See also below under +"Low Priority", on how to deal with hyphens and dashes. <h3>Medium Priority</h3> -<ul> -<li>Break hyphens and dashes. The following rules seem to be relevant: +<b>Break hyphens and dashes:</b> The following rules seem to be relevant: + <ol> <li>In English, an em-dash is used with no spaces around. Breaking before and after the dash should be possible, perhaps with a penalty > @@ -353,21 +353,73 @@ instead.)</li> be possible. As described above ("Abtei-Stadt"), this collides with hyphenation.</li> </ol> + Where to implement? In the same dynamic, lazy way like hyphenation? As -part of hyphenation?</li> -</ul> +part of hyphenation? + +<b>Incorrect calculation of extremes:</b> The minimal width of a text +block (as part of the width extremes, which are mainly used for +tables) is defined by everything between two possible breaks. A +possible break may also be a hyphenation point; however, hyphenation +points are calculated in a lazy way, when the lines are broken, and +not when extremes are calculated. So, it is a matter of chance whether +the calculation of the minimal width will take the two parts "dil-" +and "lo" into account (when "dillo" has already been hyphenated), or +only one part, "dillo" (when "dillo" has not yet been hyphenated), +resulting possibly in a different value for the minimal width. + +Possible strategies to deal with this problem: + +<ol> +<li>Ignore. The implications should be minimal. +<li>Any solution will make it neccessary to hyphenate at least some +words when calculating extremes. Since the minimal widths of all words +are used to calculate the minimal width of the text block, the +simplest approach will hyphenate all words. This would, of course, +eliminate the performace gains of the current lazy approach. +<li>The latter approach could be optimized in some ways. Examples: (i) +If a word is already narrower than the current accumulated value for +the minimal width, it makes no sense to hyphenate it. (ii) In other +cases, heuristics may be used to estimate the number of syllables, the +width of the widest of them etc. +</ol> <h3>Low Priority</h3> -<ul> -<li>Should dw::core::Content::BREAK still be used? Currently, this is - redundant to dw::Textblock::BadnessAndPenalty.</li> -<li>The calculation of badness is designed for justified text. For - other alignments, it may be modified. (TODO: document this in - detail.)</li> -<li>It should be simple to assign a larger penalty for hyphens, when - the line before is already hyphenated. This way, hyphens in - adjacent are pelalized further.</li> -</ul> +<b>Mark the end of a paragraph:</b> Should dw::core::Content::BREAK +still be used? Currently, this is redundant to +dw::Textblock::BadnessAndPenalty. + +<b>Other than justified text:</b> The calculation of badness is +designed for justified text. For other alignments, it may be +modified. The point is the definition of strechibility and for the +line. + +Consider left-aligned text. Most importantly, not the spaces between +the words, but the space on the right border is adjusted. If the +actual line width (sum of words and normal spaces, \f$W_a^b\f$ above) +equals the the ideal width (e. g. given by the browser window +width, \f$l\f$ above), this space is zero, so it is not possible to +shrink it further. For this reason, the shrinkability is now already +set to 0. + +On the other hand, there should be a strechability for the space on +the right border. However, only the spaces between the words have a +strechability; later, the differences are summed up and used to fill +the space on the right. This works, but is a bit unprecise, since the +strechability of the space on the right depends on the number of words +in the line. + +(Likewise, if you modify the code to assign a positive value for the +shrinkability for left-aligned text, the difference is summed up and +used for the right border; since this difference is negative, the +lines will, when spaces are shrunken, get too long!) + +Analogue considerations must be made vor right-aligned and centered +text. (For centered texts, there are two adjustable spaces.) + +<b>Hyphens in adjacent lines:</b> It should be simple to assign a +larger penalty for hyphens, when the line before is already +hyphenated. This way, hyphens in adjacent are penalized further. */ |