Improvements to comments on data structures and subroutines.

FossilOrigin-Name: b217e3004b58af0e777726bdd652b999ad41815261299ef4ce8f8d2f6b0afe8d

manifest

@@ -1,5 +1,5 @@
-C In\sthe\sCLI,\swhen\sdisplaying\sresults\sin\sa\scolumnar\sformat,\stake\sinto\saccount\nzero-width\sand\sdouble-width\sUnicode\scharacters.
-D 2024-09-24T00:01:47.656
+C Improvements\sto\scomments\son\sdata\sstructures\sand\ssubroutines.
+D 2024-09-25T09:33:14.835
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -768,7 +768,7 @@ F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
 F src/resolve.c b2cd748488012312824508639b6af908461e45403037d5c4e19d9b0e8195507f
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
 F src/select.c 4b14337a2742f0c0beeba490e9a05507e9b4b12184b9cd12773501d08d48e3fe
-F src/shell.c.in 732f0fba9d956854e540f8f86deba6b65710f2f24aa0aa5381fb365f28c2ca1b
+F src/shell.c.in 9b68a945f3aafc78eac1a256a4a588a9310dbc61a0cd60378c5b7a78f789af50
 F src/sqlite.h.in 77f55bd1978a04a14db211732f0a609077cf60ba4ccf9baf39988f508945419c
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 3f046c04ea3595d6bfda99b781926b17e672fd6d27da2ba6d8d8fc39981dcb54
@@ -2213,8 +2213,9 @@ F vsixtest/vsixtest.tcl 6195aba1f12a5e10efc2b8c0009532167be5e301abe5b31385638080
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9a1fc8d36b5b262f9d17a4743b4b9bb54510cf257d2d9778ebc42d5224856b1e
-R 988b7d0f85db9a0b2a0485e0d9883734
+P 47cfad71eddc6fc4414ff853ee172da72527620eee743721806072c6e0a80caa
+R 711914e97aae1631ec1aaf0c7dbc2c36
+T +closed 47cfad71eddc6fc4414ff853ee172da72527620eee743721806072c6e0a80caa
 U drh
-Z fd42c54152b4ee78f4ca90da8d2b64c2
+Z 9e5bc0454c6f58b185adbeed59d6a33c
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-47cfad71eddc6fc4414ff853ee172da72527620eee743721806072c6e0a80caa
+b217e3004b58af0e777726bdd652b999ad41815261299ef4ce8f8d2f6b0afe8d

src/shell.c.in

@@ -670,7 +670,7 @@ static void SQLITE_CDECL iotracePrintf(const char *zFormat, ...){
 }
 #endif
 
-/* Lookup table to determine the number of columns consumed by a Unicode
+/* Lookup table to estimate the number of columns consumed by a Unicode
 ** character.
 */
 static const struct {
@@ -742,9 +742,14 @@ static const struct {
 };
 
 /*
-** Return the width, in columns, of the single Unicode character c.
-** For normal characters, the answer is always 1.  But it might be 0 or 2
-** for zero-width and double-width characters.
+** Return an estimate of the width, in columns, for the single Unicode
+** character c.  For normal characters, the answer is always 1.  But the
+** estimate might be 0 or 2 for zero-width and double-width characters.
+**
+** Different display devices display unicode using different widths.  So
+** it is impossible to know that true display width with 100% accuracy.
+** Inaccuracies in the width estimates might cause columns to be misaligned.
+** Unfortunately, there is nothing we can do about that.
 */
 int cli_wcwidth(int c){
   int iFirst, iLast;
@@ -776,6 +781,8 @@ int cli_wcwidth(int c){
 /*
 ** Compute the value and length of a multi-byte UTF-8 character that
 ** begins at z[0].   Return the length.  Write the Unicode value into *pU.
+**
+** This routine only works for *multi-byte* UTF-8 characters.
 */
 static int decodeUtf8(const unsigned char *z, int *pU){
   if( (z[0] & 0xe0)==0xc0 && (z[1] & 0xc0)==0x80 ){